Freediving

Underwater diving without breathing apparatus From Wikipedia, the free encyclopedia

Freediving, free-diving, free diving, breath-hold diving, or skin diving is a mode of underwater diving that relies on breath-holding (apnea) until resurfacing rather than the use of breathing apparatus such as scuba gear. Besides the limit of breath-hold, immersion in water and exposure to high ambient pressure also have physiological effects that limit the depths and duration possible in freediving.

A freediver on the ocean floor

Examples of freediving activities are traditional fishing techniques, competitive and non-competitive freediving, competitive and non-competitive spearfishing and freediving photography, synchronised swimming, underwater football, underwater rugby, underwater hockey, underwater target shooting and snorkeling. There are also a range of competitive apnea disciplines; in which competitors attempt to attain great depths, times, or distances on a single breath.

Historically, the term free diving was also used to refer to scuba diving, due to the freedom of movement compared with surface supplied diving.[1][2][3]

History

9th century illustration of a pearl diver

In ancient times freediving without the aid of mechanical devices was the only possibility, with the exception of the occasional use of reeds and leather breathing bladders.[4] The divers faced the same problems as divers today, such as blacking out during a breath hold. Freediving was practiced in ancient cultures to gather food, harvest resources such as sponge and pearl, reclaim sunken valuables, and to help aid military campaigns.[5] In Ancient Greece, both Plato and Homer mention the sponge as being used for bathing. The island of Kalymnos was a main centre of diving for sponges. By using weights (skandalopetra) of as much as 15 kilograms (33 lb) to speed the descent, breath-holding divers would descend to depths up to 30 metres (98 ft) to collect sponges.[6] Harvesting of red coral was also done by divers.[7]

The Mediterranean had large amounts of maritime trade. As a result of shipwrecks, particularly in the fierce winter storms, divers were often hired to salvage whatever they could from the seabed.[8]

Divers were also used in warfare. Defenses against sea vessels were often created, such as underwater barricades, and hence divers were often used to scout out the seabed when ships were approaching an enemy harbor. If barricades were found, it was divers who were used to disassemble them, if possible.[9] During the Peloponnesian War, divers were used to get past enemy blockades to relay messages as well as supplies to allies or troops that were cut off,[10] and in 332 BC, during the Siege of Tyre, the city used divers to cut the anchor cables of Alexander's attacking ships.[11]

In Japan, ama divers began to collect pearls about 2,000 years ago.[12][13] For thousands of years, most seawater pearls were retrieved by divers working in the Indian Ocean, in areas such as the Persian Gulf, the Red Sea, and in the Gulf of Mannar (between Sri Lanka and India).[14] A fragment of Isidore of Charax's Parthian itinerary was preserved in Athenaeus's 3rd-century Sophists at Dinner, recording freediving for pearls around an island in the Persian Gulf.[15]

Pearl divers near the Philippines were also successful at harvesting large pearls, especially in the Sulu Archipelago. At times, the largest pearls belonged by law to the sultan, and selling them could result in the death penalty for the seller. Nonetheless, many pearls made it out of the archipelago by stealth, ending up in the possession of the wealthiest families in Europe.[16] Pearling was popular in Qatar, Bahrain, Japan, and India. The Gulf of Mexico was also known for pearling.[17] Native Americans harvested freshwater pearls from lakes and rivers like the Ohio, Tennessee, and Mississippi, while others dived for marine pearls from the Caribbean and waters along the coasts of Central and South America.[18]

In 1940, Dottie Frazier pioneered freediving for women in the United States and also began teaching classes. It was also during this time that she began to design and sell rubber suits for Navy UDT divers.[19]

Freediving activities

Recreational hunting and gathering

Spearfishing

Spearfishing is an ancient method of fishing that has been used throughout the world for millennia. Early civilizations were familiar with the custom of spearing fish from rivers and streams using sharpened sticks.[20]

Modern spearfishing makes use of elastic powered spearguns and slings, or compressed gas pneumatic powered spearguns, to strike the hunted fish. Specialised techniques and equipment have been developed for various types of aquatic environments and target fish. Spearfishing may be done using free-diving, snorkelling, or scuba diving techniques. Spearfishing while using scuba equipment is illegal in some countries. The use of mechanically powered spearguns[clarification needed] is also outlawed in some countries and jurisdictions.[citation needed] Spearfishing is highly selective, normally uses no bait and has limited by-catch.[21]

Collection of shellfish

Various cultures have collected shellfish by freediving for "possibly thousands" of years.[22][23][24] One example is the historical recreational collection of abalone in South Africa, before illegal harvesting reduced stocks to levels which resulted in recreational collection being banned indefinitely. This did not completely stop illegal harvesting, because selling illegally harvested abalone remained lucrative.[25]

Competitive breath-hold watersports

Aquathlon

Aquathlon (also known as underwater wrestling) is an underwater sport where two competitors wearing masks and fins wrestle underwater in an attempt to remove a ribbon from each other's ankle band in order to win the bout. The "combat" takes place in a 5-metre (16 ft) square ring within a swimming pool, and is made up of three 30-second rounds, with a fourth round played in the event of a tie. The sport originated during the 1980s in the former USSR (now Russia) and was first played at international level in 1993. It was recognised by the Confédération Mondiale des Activités Subaquatiques (CMAS) in 2008.[26][27][28][29]

Competitive spearfishing

Competitive spearfishing is defined by the world governing body CMAS as "the hunting and capture of fish underwater without the aid of artificial breathing devices, using gear that depends entirely on the physical strength of the competitor." They publish a set of competition rules that are used by affiliated organisations.[30][31]

Synchronised swimming

A member of the Japanese team is thrown up in the air by other members under the water during the team's free routine at the 2013 French Open.

Synchronized swimming is a hybrid form of swimming, dance, and gymnastics, consisting of swimmers (either solos, duets, trios, combos, or teams) performing a synchronized routine of elaborate moves in the water, accompanied by music. Synchronized swimming demands advanced water skills, and requires great strength, endurance, flexibility, grace, artistry and precise timing, as well as exceptional breath control when upside down underwater. During lifts swimmers are not allowed to touch the bottom.[32]

Traditionally it was a women's sport, but following the addition of a new mixed-pair event, FINA World Aquatics competitions are open to men since the 16th 2015 championships in Kazan, and the other international and national competitions allow male competitors in every event. However, men are currently still barred from competing in the Olympics. Both USA Synchro and Synchro Canada allow men to compete with women. Most European countries also allow men to compete, and France even allows male only podiums, according to the number of participants. In the past decade, more men are becoming involved in the sport and a global biannual competition called Men's Cup has been steadily growing.[citation needed]

Swimmers perform two routines for the judges, one technical and one free, as well as age group routines and figures. Synchronized swimming is both an individual and team sport. Swimmers compete individually during figures, and then as a team during the routine. Figures are made up of a combination of skills and positions that often require control, strength, and flexibility. Swimmers are ranked individually for this part of the competition. The routine involves teamwork and synchronization. It is choreographed to music and often has a theme. Synchronized swimming is governed internationally by FINA (Fédération Internationale de Natation).[citation needed]

Underwater hockey

Two players compete for the puck in underwater hockey.

Underwater hockey (also called octopush, mainly in the United Kingdom) is a globally played limited-contact sport in which two teams compete to manoeuvre a hockey puck across the bottom of a swimming pool into the opposing team's goal by propelling it with a hockey stick. The sport originated in England in 1954 when Alan Blake, the founder of the newly formed Southsea Sub-Aqua Club, invented the game he called octopush to keep the club's members interested and active during the cold winter months, when open-water diving is limited.[33] Underwater hockey is now played worldwide, governed by the Confédération Mondiale des Activités Subaquatiques (CMAS).[34] The first Underwater Hockey World Championship was held in Canada in 1980, after a planned championship in 1979 was scuttled by international politics and apartheid.[citation needed]

Underwater football

US Navy Students playing underwater football

Underwater football is a two-team underwater sport that shares common elements with underwater hockey and underwater rugby. As with both of those games, it is played in a swimming pool with snorkeling equipment (mask, snorkel, and fins). The goal of the game is to manoeuvre (by carrying and passing) a slightly negatively buoyant ball from one side of a pool to the other by players who are completely submerged underwater. Scoring is achieved by placing the ball (under control) in the gutter on the side of the pool. Variations include using a toy rubber torpedo as the ball, and weighing down buckets to rest on the bottom and serve as goals.[citation needed]

It is played in the Canadian provinces of Alberta, Manitoba, Newfoundland and Labrador, and Saskatchewan.[35]

Underwater rugby

Underwater rugby is an underwater team sport. During a match, two teams try to score a negatively buoyant ball (filled with saltwater) into the opponents' goal at the bottom of a swimming pool. It originated from within the physical fitness training regime existing in German diving clubs during the early 1960s and has little in common with rugby football except for the name. It was recognised by CMAS in 1978 and was first played as a world championship in 1980.[citation needed]

Underwater target shooting

Underwater target shooting is an underwater sport that tests a competitors' ability to accurately use a speargun via a set of individual and team events conducted in a swimming pool using free diving or apnea technique. The sport was developed in France during the early 1980s and is currently practised mainly in Europe. It is known as Tir sur cible subaquatique in French and as Tiro al Blanco Subacuático in Spanish.

Competitive apnea

Monofin freediver

Competitive freediving is currently governed by two world associations: AIDA International[36] and Confédération Mondiale des Activités Subaquatiques (CMAS). Historically, there were two more organisations that regulated freediving records and activities — International Association of Freedivers (IAFD) and Freediving Regulations and Education Entity (FREE).[37][38] Each organization has its own rules on recognizing a record attempt which can be found on the organization's website. Alongside competitive disciplines, there are record disciplines — disciplines that are not held in competitions, that are just for setting world records. There is a third organization, Guinness, which in addition to AIDA and CMAS presides over record disciplines.[citation needed]

Almost all types of competitive freediving are individual sports based on the best individual achievement. Exceptions to this rule are the bi-annual AIDA Team World Championship, where the combined score of the team members makes up the team's total points, and Skandalopetra diving competitions held by CMAS, the only truly 'team' event in freediving for which teams are formed by two athletes: one acting as the diver (βουτηχτής, voutichtis) and the other acting as an assistant (κολαουζέρης, kolaouzeris).[citation needed]

Disciplines

There are currently eleven recognized disciplines defined by AIDA and CMAS, and a dozen more that are only practiced locally.[clarification needed][citation needed] All disciplines can be practiced by both men and women, and only CMAS currently distinguishes records in fresh water from those at sea. The disciplines of AIDA can be done both in competition and as a record attempt, with the exception of variable weight and no limits, which are both solely for record attempts. For all AIDA depth disciplines, the depth the athlete will attempt is announced before the dive; this is accepted practice for both competition and record attempts. Most divers choose monofin (MF) over bifins (BF) where there is a choice.[citation needed]

More information Discipline, Measure­ment ...
Discipline Measure­ment AIDA[39] CMAS[40] Description
open water pool open water pool
Constant weight apnea (CWT)depthGreen tickYGreen tickY Maximum depth following a guide line. The line to act solely as a guide and only a single hold of the rope to stop the descent and start the ascent is permitted. Dropping dive weights is not permitted. Both bi-fins and monofin are permitted and the technique is irrelevant.
Constant weight bi-fins (CWT BF, CWTB)depthGreen tickYGreen tickY As for CWT above but monofins are not permitted and the athlete is prohibited to use a dolphin kick for his / her propulsion.
Constant weight without fins (CNF)depthGreen tickYGreen tickY As for CWT above but no swimming aids such as fins are permitted. This discipline is the most recently recognised discipline having been recognised by AIDA since 2003.
Dynamic apnea without fins (DNF)horizontal distanceGreen tickYGreen tickYGreen tickY Maximum distance underwater, in a pool, no swimming aids such as fins are permitted (AIDA).
Dynamic apnea with fins (DYN)horizontal distanceGreen tickYGreen tickYGreen tickY Maximum horizontal distance on one breath in a pool. Monofin or bi-fins are permitted and the technique is irrelevant.
Dynamic apnea with bifins (DYN BF, DYNB)horizontal distanceGreen tickYGreen tickY Same as DYN above but monofins are not permitted and the athlete is prohibited to use a dolphin kick for his / her propulsion.
Free immersion apnea (FIM)depthGreen tickYGreen tickY Maximum depth following a vertical line. The line may be used to pull down to depth and back to the surface. No ballast or fins are permitted. It is known for its ease compared with the Constant Weight disciplines, while still not permitting the release of weights.
Jump blue (JB, also the cube)horizontal distanceRed XNGreen tickY Maximum distance covered around a 15-metre square at a depth of 10 metres. Monofin, bi-fins or no fins are all permitted. Sled may be used for descent.
No-limits apnea (NLT)depthGreen tickYRed XN Any means of breath-hold diving to depth and return to the surface is permitted provided that a guideline is used to measure the distance. Most divers use a weighted sled to descend and an inflatable bag to ascend. It is important to note that new attempts are not recognised due to the level of danger presented to divers[41]
Skandalopetradepth & min. timeRed XNGreen tickY The only true team event in freediving. Diver 1 descends, usually assisted by a stone or marble slab attached to a rope, while Diver 2 waits on the surface. Diver 1 reaches the target depth and is hauled to the surface by Diver 2 using only muscle power. No diving mask, suit or fins are permitted, only nose clip.
Static apnea (STA)max. timeGreen tickYGreen tickYGreen tickYGreen tickY Timed breathhold endurance while floating on the surface or standing on the bottom. Usually in a pool.
Static apnea with pure oxygen (STA O2)max. timeRed XNRed XN Timed breathhold endurance, pre-breathing 100% oxygen for up to 30 minutes prior to the breathhold is permitted. Usually in a pool. Although no longer recognised by either AIDA or CMAS there were three instances of records being approved by AIDA.
Speed-endurance apnea (S&E apnea)[42]min. timeRed XNGreen tickY Shortest time over a fixed, underwater distance. An endurance sub-discipline is swum in fractions of a pool length alternating apnoea swimming with passive recovery at the intervals. Disciplines are SPE – 100m speed apnoea, END 16x50 – 800m and END 8x50 – 400m endurance apnoea.
Variable weight apnea without fins (VNF)depthRed XNGreen tickY Descent is assisted by a weighted sled sliding down a line, the ascent may be by pulling up along the line or swimming without fins.
Variable weight apnea (VWT)depthGreen tickYGreen tickY Descent is assisted by a weighted sled sliding down a line, the ascent may be either by:
1.) pulling up along the line or swimming with or without fins under AIDA rules
2.) swimming with fins under CMAS rules.
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Herbert Nitsch, World Record Holder Freediver
Deep-Sea World Cup Camotes Islands, Philippines; Constant Weight No-fins (CNF); Agata Załęcka 2025
Overview of the above disciplines[43][44][42]
More information Discipline, Aids permitted ...
Discipline Aids permitted Weight
change
permitted?
Descent Ascent
CNF None
or weight
None No
CWT BF / MF
and/or weight
BF / MF No
CWT BF BF
and/or weight
BF No
DNF
DYN
DYN BF
FIM Rope
or none
Rope
or none
No
JB Sled and/or
BF / MF or none
BF / MF
or none
Sled only
NLT (No Limit) (Only AIDA) Any Any Yes
Skandalopetra Stone Hauled up Yes
STA
STA O2
S&E Apnoea
VNF (only CMAS) Sled Rope
or none
Yes
VWT Sled BF / MF
or rope
Yes
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World records

The best official result in static apnea is the Guinness WR of 11:54 by Branko Petrović in 2014, a freediver who has results over 10 minutes under both AIDA and CMAS.[citation needed] The best no limits result is 253.2m by Herbert Nitsch in 2012; his intention of having the dive sanctioned by AIDA fell through due to a sponsoring conflict.[citation needed] After 2001, AIDA International no longer separated the records achieved in fresh water from those in the sea.[citation needed]

CMAS recognized world records

As of 1 January 2024, the CMAS recognized world records are:[45]

More information Discipline, Gender ...
Discipline Gender Depth
[m]
Distance
[m]
Time Name/Country Date Place
Static apneaSTAMen10:45.000 Branko Petrović (SRB)2017-11-11Subotica, Serbia
Women08:53.150 Veronika Dittes (AUT)2017-06-15Cagliari, Italy
Dynamic apnea with finDYNMen321.43 Mateusz Malina (POL)2022-06-15Belgrade, Serbia
Women275.36 Mirela Kardašević (CRO)2022-06-15Belgrade, Serbia
under iceMen175 Arthur Guérin-Boëri (FRA)2017-03-11Lake Sonnanen, Finland
Women140 Valentina Cafolla (CRO)2024-02-23Lake Anterselva, Italy[46]
open waterMen200 Sertan Aydin (TUR)
Women
Dynamic apnea with bifinsDBFMen274.70 Guillaume Bourdila (FRA)2022-06-13Belgrade, Serbia
Women250.00 Mirela Kardašević (CRO)2022-06-13Belgrade, Serbia
Dynamic apnea without finsDNF-50Men236 Guillaume Bourdila (FRA)2019-06-19Istanbul, Turkey
Women210 Julia Kozerska (POL)2022-06-12Belgrade, Serbia
DNF-25Men220.70 Vanja Peles (CRO)2021-03-28Sisak, Croatia
Women206.20 Mirela Kardasevic (CRO)2021-03-28Sisak, Croatia
Speed 100 m.SPEMen00:30.350 Malte Striegler (GER)2018-06-15Lignano, Italy
Women00:35.860 Vera Yarovitskaya (RUS)2017-06-15Cagliari, Italy
EnduranceEND16x50Men09:10.030 Max Poschart (GER)2019-06-19Istanbul, Turkey
Women10:41.120 Evgeniia Kozyreva (RUS)2021-06-23Belgrade, Serbia
END8x50Men03:05.720 Mikhail Drozdov (RUS)2019-06-22Istanbul, Turkey
Women04:10.190 Chiara Zaffaroni (ITA)2023-05-10Kuwait
END4x50Men
Women01:33.860 Chiara Zaffaroni (ITA)2023-05-11Kuwait
Jump blue apnea with finsat seaMen201.61 Arthur Guérin-Boëri (FRA)2015-10-09Ischia, Italy
Women190.48 Alessia Zecchini (ITA)2015-10-09Ischia, Italy
fresh waterMen170 Alfredo Leonidas Rosado Estrada (ECU)
Women132.92 Gilda Rivadeneria Montalvo (ECU)
Constant weight with finsat seaMen136 Alexey Molchanov (RUS)2023-08-23Roatan, Honduras
Women122 Alenka Artnik (SLO)2021-07-21Long Island, Bahamas
fresh waterMen80 Michele Tomasi (ITA)
Women57 Tanya Streeter (UK)1998-12-28Ocala, Fl, USA
Constant weight with bifins (CWT BF)at seaMen124 Alexey Molchanov (RUS)2023-08-25Roatan, Honduras
Women106 Alenka Artnik (SLO)2021-09-30Kaş, Turkey
fresh waterMen75 Michele Tomasi (ITA)
Women
Constant weight without finsat seaMen100 Alexey Molchanov (RUS)2023-08-23Roatan, Honduras
Women78 Kateryna Sadurska (UKR)2023-08-24Roatan, Honduras
fresh waterMen65 Michal Rišian (CZE)2016-07-10Weyregg, Austria
Women
Free immersion apneaat seaMen132 Petar Klovar (CRO)2022-10-04Kaş, Turkey
Women72 Alessia Zecchini (ITA)2021-07-17Long Island, Bahamas
Variable weight apnea monofinat seaMen131 Homer Leuci (ITA)2012-09-11Soverato, Italy
Women116 Lena Balta (SER)2022-06-25Sharm el Sheik, Egypt
Variable weight apnea bifinsat seaMen130 William Winram (SWI)2021-10-21Sharm el Sheik, Egypt
Women-
Variable weight apnea without fins (VNF)at seaMen140 William Winram (SWI)2023-12-11Sharm el Sheik, Egypt
Women106 Şahika Ercümen (TUR)2023-10-17Hatay, Turkey
Skandalopetraat seaMen112 Andreas Güldner (GER)2014-06-26Red Sea, Egypt
Women68.9 Karol Meyer (BRA)2012Bonaire, Caribbean
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AIDA recognized world records

As of 26 July 2023, the AIDA recognized world records are:[47][48][49]

More information Discipline, Gender ...
Discipline Gender Depth [m] Distance [m] Time Name Date Place
Static apnea (STA)Men11 min 35 sec Stéphane Mifsud (FRA)2009-06-08Hyères, Var, France
Women9 min 22 sec Heike Schwerdtner (GER)2025-05-04Stockholm, Sweden
Dynamic apnea with fins (DYN)Men316.53 Mateusz Malina (POL)[50]2019-06-22Turku, Finland
Women280 Zsófia Törőcsik (HUN)2025-07-02Wakayama, Japan
Dynamic apnea with bifins (DYNB)Men298 Guillaume Bourdila (FRA)2025-06-28Wakayama, Japan
Women208 Kardasevic Mirela (CRO)2019-03-07Moscow, Russia
Dynamic apnea without fins (DNF)Men250 Mateusz Malina (POL)2022-05-01Dębica, Poland
Women213 Julia Kozerska (POL)2023-06-13Seogwipo, South Korea
Constant weight apnea (CWT)Men133 Alexey Molchanov (RUS)2023-07-22Dean's Blue Hole, Long Island Bahamas
Women123 Alessia Zecchini (ITA)2023-04-24Camotes Island, Philippines
Constant weight apnea with bifins (CWTB)Men126 Alexey Molchanov (RUS)2025-09-26Limassol, Cyprus
Women111 Alenka Artnik (SVN)2023-07-30Dean's Blue Hole, Long Island Bahamas
Constant weight apnea without fins (CNF)Men103 Petar Klovar (CRO)2025-05-26Sharm el-Sheikh, Egypt
Women73 Alessia Zecchini (ITA)2016-04-26Dean's Blue Hole, Long Island Bahamas
Free immersion apnea (FIM)Men133 Alexey Molchanov (RUS)2023-07-21Dean's Blue Hole, Long Island Bahamas
Women103 Sanda Delija (HRV)2025-05-04Mabini, Philippines
Variable weight apnea (VWT)Men156 Alexey Molchanov (RUS)2023-03-28Bonaire, Caribbean
Women130 Nanja van den Broek (NED)2015-10-18Sharm el-Sheikh, Egypt
No Limit apnea (NLT)Men214 Herbert Nitsch (AUT)2012-06-06Santorini, Greece
Women160 Tanya Streeter (UK)2002-08-17Turks and Caicos
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More information Discipline, Gender ...
Discipline Gender Points Team / Individual Date Place
AIDA teamMen840.6 CRO
Goran Čolak, Božidar Petani, Veljano Zanki
2012-09-16Nice, France[51][52]
Women
Men313.3 William Trubridge (NZL)2010-07-06Okinawa, Japan[53][54]
Women
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Guinness recognized world records

The following table only includes those disciplines that are modifications of existing AIDA or CMAS disciplines and Guinness-exclusive (as it recognizes and inherits some AIDA/CMAS records) or Guinness-conceived (CMAS and AIDA do/did sanction at some time[clarification needed]) disciplines.

As of 25 February 2018:

More information Discipline, Gender ...
Discipline Gender Depth [m] Distance [m] Time Name Date Place
STA O2Men24:11 Budimir Šobat (CRO)24 February 2018Zagreb
Women18:32 Karol Meyer (BRA)10 July 2009Florianopolis
DYN under iceMen175details under CMAS world records
Women125
DNF under iceMen84 Nik Linder (GER)Feb 2013Weissensee[55][56]
Women
DNF under ice (no diving suit)Men81 David Vencl (CZ)Feb 2021Lahošť lake
Women50 Johanna Nordblad (FIN)Mar 2015Päijänne[57]
NLT under iceMen65 Andreas Pap (SRB)Feb 2013Weissensee[55]
Women
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Recreational

Recreational freediving at the Blue Hole in the Red Sea

Freediving as a recreational activity is widely practiced and differs significantly from scuba diving. Although there are risks to all freediving activities, it can be acceptably safely practiced at a wide range of skill levels from the average snorkeler to the professional freediver. Compared to scuba diving, freediving offers:[citation needed]

  • Freedom from cumbersome equipment and short preparation times.
  • Low cost.
  • It is quiet and does not disturb fish, the noise of breathing and bubbles can be quite loud on open circuit scuba though rebreathers are much quieter.
  • Mobility and speed, but for a much more limited period.
  • No decompression stops required for deep dives, although it is possible to get decompression sickness, or taravana, from repetitive deep free-diving with short surface intervals.[58] This is balanced against much shorter dive times.
  • The lack of exhaled air bubbles gives better visibility during ascent.
  • Accessibility, if the site can be walked to it can, potentially, be dived.[clarification needed]
  • Appropriately skilled and fit freedivers can go as deep, or deeper than, recreational scuba divers, the depth being limited only by the willingness to accept the risks; scuba diving is restricted by the level of certification.[dubious discuss][relevant?]

Freshwater springs and other caves, often with excellent visibility, have been freedived but with greater risks. Diving into water with restricted access to the surface is very different from diving in open water. The time available to a freediver to solve problems underwater before hypoxia sets in is severely restricted in comparison with scuba, and scuba diving under an overhead is not recommended without an independent emergency gas supply. Freediving into confined cave systems has resulted in several deaths.[citation needed] Cave freediving is strongly discouraged in basic freediver safety training.[59]

Physiology

Human physiology of freediving is the physiological influences of the underwater environment on the human breath hold ambient pressure diver, and adaptations to operating underwater. It, therefore, includes the range of physiological effects generally limited to human freediving. Several factors influence the diver, including immersion, exposure to the water, the limitations of breath-hold endurance, variations in ambient pressure, and sensory impairment. All of these may affect diver performance and safety.[60]

Immersion affects fluid balance, circulation and work of breathing.[61][62] Exposure to cold water can result in the harmful cold shock response,[63][64] the helpful diving reflex and excessive loss of body heat.[65][66][67][68] Breath-hold duration is limited by oxygen reserves, the response to raised carbon dioxide levels, and the risk of hypoxic blackout, which has a high associated risk of drowning.[69][70][71]

Large or sudden changes in ambient pressure have the potential for injury known as barotrauma.[60][72] Metabolically inactive gases are absorbed by the tissues and may have narcotic or other undesirable effects, and must be released slowly to avoid the formation of bubbles during decompression.[73]

The underwater environment also affects sensory input, which can impact on safety and the ability to function effectively at depth.[61]

Recent human adaptation

In addition to general adaptations within the human species, freediving is an example of an activity that has been directly affected by recent human evolution. The Bajau, or "Sea Nomads," have engaged in freediving for thousands of years, and natural selection has led to larger spleen sizes. This serves as an oxygen reservoir when diving. It is hypothesized that other isolated diving populations globally may have experienced the same selection.[74]

Techniques

Breath-holding ability, and hence dive performance, is a function of on-board oxygen stores, scope for metabolic rate reduction, efficient oxygen utilization, and hypoxia tolerance.[75] Athletes attempt to accomplish this in various ways. Some divers use "packing", which increases lung volume beyond normal total lung capacity.[76] In addition, training is allocated to enhance blood and muscle oxygen stores, to a limited extent.[clarification needed] Most divers rely on increasing fitness by increasing CO2 tolerance and lung capacity. Simple breath-holding practice is highly effective for the build-up of tolerance to CO2 and to some degree increased lung capacity. In an interview on the radio talk show Fresh Air, journalist James Nestor, author of the book Breath: The New Science of a Lost Art,[77] stated: "Some divers have a lung capacity of 14 liters, which is about double the size for a typical adult male. They weren't born this way. ... They trained themselves to breathe in ways to profoundly affect their physical bodies."[78][dubious discuss]

Before competition attempts, freedivers perform a preparation sequence, which usually consists of physical stretching, mental exercise and breath exercise. It may include a succession of variable length static apnea and special purging deep breaths. Results of the preparation sequence are slower metabolism, lower heart and breathing rates, lower levels of carbon dioxide in the bloodstream,[79] and overall mental equilibrium.[citation needed]

Lung packing

Technically known as glossopharyngeal insufflation, lung packing or buccal pumping is a technique for inflating the lungs beyond their normal isobaric total capacity, which is used to delay the compression of the lungs at by hydrostatic pressure, allowing a greater depth to be reached, and provide a slightly larger reserve of oxygen for the dive. After full normal inspiration, the diver fills the mouth with air, with the glottis closed, then opens the glottis and forces the air from the mouth into the lung, then closes the glottis to hold in the air. This is repeated several times. Lung packing can increase the volume of air in the lungs by up to 50% of vital capacity. The pressure induced will reduce the volume of blood in the chest, which will increase the space available for air. The gas in the lungs is also compressed. Pressures of about 75 millimetres of mercury (100 mbar) have been reported.[80] Lung packing has been associated with short-term haemodynamic instabilities, which might contribute toward triggering blackout.[81]

Recovery breathing

Also known as hook breathing. This is a technique used by free divers on surfacing to reduce the risk of surface blackout. A partial exhalation is made, followed by a quick inhalation; then the diver closes the airway and pressurises for a few seconds as if about to cough. This behavior is repeated a few times over the first 30 seconds or so on the surface. The aim is to keep thoracic pressure slightly raised to artificially raise arterial oxygen partial pressure or prevent it from dropping in the critical seconds until newly oxygenated blood can reach the brain and thereby prevent surface blackout. This is the same technique used by pilots during high-g maneuvers, as well as by mountaineers at high altitude.[82][83]

Training

There is no requirement by law that free-divers are required to do formal freediving training or be certified, but due to the risks inherent to the sport, freediving without knowledge or training can pose a greater risk to life. The free-diving courses contain three components: theory studies, confined water sessions generally conducted in a swimming pool, and open water sessions in the ocean or other large body of fresh or salt water.[84][85]

Training for breathhold endurance can take many forms, some of which can be performed on land. One training exercise is the apnea walk. This consists of a preparation "breathe-up", followed by a short (typically 1 minute) breath hold taken at rest. Without breaking the hold, participants then begin walking as far as possible until it becomes necessary to breathe again. Some athletes can do close to 400 meters in training this way.[citation needed]

This form of training is good for accustoming muscles to work under anaerobic conditions, and for tolerance to carbon dioxide build-up in the circulation. It is also easy to gauge progress, as increasing distance can be measured.[citation needed]

Certification

There are several training agencies that provide certification in freediving at various levels from beginner to instructor. Some, like AIDA and Molchanovs, are focused exclusively on freediving, particularly competitive aspects, while others, like PADI and SSI, are primarily international recreational scuba training agencies that have branched out into recreational freediving. All of these agencies will provide instruction and practical training in aspects of safety, basic freediving physiology theory and practical techniques.[86]

Safety

Freedivers are encouraged by certification and sporting organisations to dive only with a 'buddy' who accompanies them, observing from in the water at the surface, and ready to dive to the rescue if the diver loses consciousness during the ascent. This is only reasonably practicable if the water clarity allows observation, and the buddy is capable of safely reaching the diver. In poor visibility the diver can clip onto the downline with a buddy line. Signals can be transmitted on the downline and it can be used to find the diver. Spearfishers can use a surface marker buoy for the same purpose. Due to the nature of the sport, the risks of freediving can be reduced by strict adherence to safety measures as an integral part of the activity, but cannot be eliminated. Competition rules may require all participants to be certified and adept in rescue and resuscitation.[87][88]

Hazards, consequences and risk

The most obvious hazard is lack of access to air for breathing – a necessity for human life. This can result in asphyxia from drowning if the diver does not reach the surface while still capable of holding their breath and resuming breathing. The risk depends on several factors, including the depth, duration and shape of the dive profile.[89]

Latent hypoxia is a specific hazard of deeper freedives. This effect can cause hypoxic blackout during surfacing.[90]

Freediving blackout, breath-hold blackout,[91] or apnea blackout is a class of hypoxic blackout, a loss of consciousness caused by cerebral hypoxia towards the end of a breath-hold (freedive or dynamic apnea) dive, when the swimmer does not necessarily experience an urgent need to breathe and has no other obvious medical condition that might have caused it. It can be provoked by hyperventilating just before a dive, or as a consequence of the pressure reduction on ascent, or a combination of these. Victims are often established practitioners of breath-hold diving, are fit, strong swimmers and have not experienced problems before.[72][71][70]

Divers and swimmers who black out or grey out underwater during a dive will usually drown unless rescued and resuscitated within a short time.[92] Freediving blackout has a high fatality rate, and mostly involves males younger than 40 years, but is generally avoidable. Risk cannot be quantified, but is clearly increased by any level of hyperventilation.[69]

Freediving blackout can occur on any dive profile: at constant depth, on an ascent from depth, or at the surface following ascent from depth and may be described by a number of terms depending on the dive profile and depth at which consciousness is lost. Blackout during a shallow dive differs from blackout during ascent from a deep dive in that blackout during ascent is precipitated by depressurisation on ascent from depth while blackout in consistently shallow water is a consequence of hypocapnia following hyperventilation.[70][93]

There is also a wide range of environmental hazards possible specific to the site and water and weather conditions at the time of diving, and there may be other hazards specific to the freediving activity, such as spearfishing.[94]

Failing to respond to physiological warning signals, or crossing the mental barrier by strong will, may lead to blackout underwater or on reaching the surface.[12][95] Trained freedivers are well aware of this and competitions must be held under strict supervision and with competent first-aiders on standby.[96] However, this does not eliminate the risk of blackout.[87]

Competition safety

Following the deaths of two freedivers in competitions, AIDA has a system set up for monitoring and if necessary, recovering competitors who lose consciousness underwater. As of 2022 the incidence of adverse events in depth competitions varies between 3 and 4% of competition dives. This rate is considered relatively low and is expected during competitions where divers push their breath-hold limits. Almost all of these divers are successfully assisted and recover completely. There is a much lower incidence of more serious injuries.[97]

Safety divers

Deep safety principles for freediving with counter weight

The safety team is usually made up of volunteers, or paid staff in some major events, and is supervised by the Chief of Safety. Each competitor is monitored by a team of breath-hold safety divers who will descend in time to meet the competitor during their ascent, and monitor them for the rest of the ascent. They will intervene if necessary, typically by securing the competitor's airway and swimming them up to the surface. The first safety diver will meet the competitor at somewhere around 1/3 to 1/4 of the target depth, usually with a maximum of 30m. The second will meet them about 10m shallower, and a third will be on standby in case of an emergency. The work can be challenging as many dives are done in a day, so the team of safety divers is usually rotated to ensure that they are not overtasked.[97] Scuba divers and scooter freedivers may also be part of the safety team.[98]

In case of a deeper incident, the competitor is clipped to the downline for the duration of the dive, which can be rapidly raised by the surface support team, which includes a medical support group.[97]

Statistics and notable accidents

Nicholas Mevoli, a diver from New York died on 17 November 2013 after losing consciousness on surfacing from a 3-minute 38 second dive to a depth of 72 metres (236 ft) during an official record attempt in the "constant weight without fins" event. He had previously reached greater depths and longer times in other disciplines.[99]

On 22 July 2017, Irish safety diver Stephen Keenan died during a dive in Dahab, Egypt. He was the safety diver for Italian freediver Alessia Zecchini, who was attempting to swim through the Arch of the Blue Hole (Red Sea). For reasons that remain unclear, Keenan began his descent approximately 20 seconds later than planned, causing him to miss the scheduled meeting point with Zecchini. He eventually reached her and assisted her ascent to the surface. Shortly afterward, Keenan lost consciousness and was later found floating face down in the water.[100]

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