Freediving

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Freediver with monofin, ascending

Freediving, free-diving, or free diving is a form of underwater diving that relies on a diver's ability to hold his or her breath until resurfacing rather than on the use of a breathing apparatus such as scuba gear. Examples include breath-hold spear fishing, freedive photography, recreational breath-hold diving, apnea competitions, freediving short sections of underwater passages when caving, and to some degree, snorkeling. The activity that garners the most public attention is the extreme sport of competitive apnea in which competitors attempt to attain great depths, times, or distances on a single breath.

History[edit]

See also: Sponge diving
Natural sponges have been harvested by freedivers near the Greek island of Kalymnos since at least the time of Plato.

Underwater diving was practised in ancient cultures to gather food, harvest resources like sponge and pearl, reclaim sunken valuables, and to help aid military campaigns. In ancient times free diving without the aid of mechanical devices was the only possibility, with the exception of the occasional use of reeds and leather breathing bladders.[1] The divers faced the same problems as divers today, such as decompression sickness and blacking out during a breath hold. Because of these dangers, diving in antiquity could be quite deadly.

Underwater diving for commercial, rather than recreational purposes may have begun in Ancient Greece, since 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) for as much as 5 minutes to collect sponges.[2] Sponges weren't the only valuable harvest to be found on the sea floor; the harvesting of red coral was also quite popular. A variety of valuable shells or fish could be harvested in this way creating a demand for divers to harvest the treasures of the sea, which could also include the sunken riches of other seafarers. The Ama Divers from Japan began to collect pearls about 2,000 years ago.[3][4]

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.[5] Divers would swim down to the wreck and choose the most valuable pieces to salvage. These salvage divers faced many dangers on the job, and as a result, laws, such as the Lex Rhodia, were enacted that awarded a large percentage of the salvage to the divers; in wrecks deeper than 50 feet, divers received one third of the salvage and in wrecks deeper than 90 feet they received half.

Divers were also used in warfare. Defenses against sea vessels were often created, such as underwater barricades aimed at sinking enemy ships. As the barricades were hidden under the water, divers were often used to scout out the sea bed when ships were approaching an enemy harbor. Once these barricades were found it was divers who were used to disassemble them, if possible.[6] 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 by the blockade.[7] On top of all that these ancient frogmen were used as saboteurs, drilling holes in enemy hulls, cutting ships rigging and mooring.

Overview[edit]

Freediving is a technique used with various aquatic activities. Examples of recognized freediving activities are (non-) competitive freediving, (non-) competitive spearfishing, freediving photography and mermaid shows. Less recognized examples of freediving include, but are not limited to, synchronized swimming, underwater rugby, underwater hockey, underwater hunting other than spearfishing, underwater target shooting and snorkeling. The discussion remains whether freediving is only a synonym for breath-hold diving or whether it describes a specific group of underwater activities. The term 'freediving' is often associated with competitive breath-hold diving or competitive apnea.

Competitive[edit]

Competitive freediving is currently governed by two world associations: AIDA International (International Association for Development of Apnea)[8] and CMAS (World Underwater Federation). Most types of competitive freediving have in common that it is an individual sport based on the best individual achievement. An exception to this rule is the bi-annual World Championship for Teams, held by AIDA, where the combined score of the team members makes up the team's total points. There are currently nine disciplines used by official governing bodies and a dozen disciplines that are only practiced locally. In this article, the recognized disciplines of AIDA and CMAS will be described. All disciplines can be done by both men and women and, while done outdoors, no differences in the environment between records are recognized any longer. 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 done solely as record attempts.

The following official disciplines are recognized by AIDA, CMAS, or both.

Pool disciplines[edit]

Monofin freediver holding his breath and swimming underwater
  • Static apnea is timed breath holding and is usually attempted in a pool (AIDA).[8]
  • Dynamic apnea with fins – This is underwater swimming in a pool for distance. For this discipline the athlete can choose whether to use bi-fins or the monofin (AIDA, CMAS).[8]
  • Dynamic apnea without fins – This is underwater swimming in a pool for distance without any swimming aids like fins (AIDA).[8]

Depth disciplines[edit]

For all AIDA disciplines, the depth the athlete will attempt is announced before the dive. This is accepted practice for both competitions and record attempts.

  • Constant weight apnea. The athlete has to dive to the depth following a guide line that he or she is not allowed to actively use during the dive. The ‘Constant Weight’ (French: "poids constant") refers to the fact that the athlete is not allowed to drop any diving weights during the dive. Both bi-fins and monofin can be used during this discipline (AIDA).
  • Constant weight apnea without fins follows the identical rules as Constant Weight, except no swimming aids such as fins are allowed. This discipline is the youngest discipline within competitive freediving and is recognised by AIDA since 2003 (AIDA).
  • Free immersion apnea is a discipline in which the athlete uses the vertical guiderope to pull him or herself down to depth and back to the surface. It is known for its ease compared with the Constant Weight disciplines, while the athlete is still not allowed to release weights (AIDA).
  • Variable weight apnea is a record discipline that uses a weighted sled for descent. Athletes return to the surface by pulling themselves up along a line or swimming while using their fins (AIDA).
  • No-limits apnea is a record discipline that allows the athlete to use any means of breath-hold diving to depth and return to the surface as long as a guideline is used to measure the distance. Most divers use a weighted sled to dive down and use an inflatable bag to return to the surface (AIDA).
  • The jump blue also called "the cube" is a discipline in which an athlete has to descend and swim as far as possible in a cubic form of 15 x 15 meters (CMAS).

Each organization has its own rules on recognizing an attempt. These can be found on the website from the respective organizations.

Herbert Nitsch, World Record Holder Freediver

AIDA recognized world records[edit]

As of 19 July 2014, the AIDA recognized world records are:[9]

Discipline Gender Distance [m] Time Name Date Place
Constant weight apnea (CWT) Men 128 - Alexey Molchanov 2013-09-19 Kalamata, Greece
Constant weight apnea (CWT) Women 101 - Natalia Molchanova 2011-09-22 Kalamata, Greece
Constant weight apnea without fins (CNF) Men 101 - William Trubridge 2010-12-16 Dean's Blue Hole, Long Island Bahamas
Constant weight apnea without fins (CNF) Women 70 - Natalia Molchanova 2014-05-15 Dahab, Egypt
Free immersion apnea (FIM) Men 121 - William Trubridge 2011-04-10 Dean's Blue Hole, Long Island Bahamas
Free immersion apnea (FIM) Women 91 - Natalia Molchanova 2013-09-21 Kalamata, Greece
Variable weight apnea (VWT) Men 145 - William Winram 2013-09-03 Sharm el-Sheikh, Egypt
Variable weight apnea (VWT) Women 127 - Natalia Molchanova 2012-06-06 Sharm el-Sheikh, Egypt
No-limits apnea (NLT) Men 214 - Herbert Nitsch 2007-06-14 Spetses, Greece
No-limits apnea (NLT) Women 160 - Tanya Streeter 2002-08-17 Turks and Caicos
Static apnea (STA) Men - 11 min 35 sec Stéphane Mifsud 2009-06-08 Hyères, Var, France
Static apnea (STA) Women - 9 min 02 sec Natalia Molchanova 2013-06-29 Belgrade, Serbia
Dynamic apnea with fins (DYN) Men 281 - Goran Čolak 2013-06-28 Belgrade, Serbia
Dynamic apnea with fins (DYN) Women 234 - Natalia Molchanova 2013-06-28 Belgrade, Serbia
Dynamic apnea without fins (DNF) Men 225 - Goran Čolak 2013-11-21 Pančevo, Serbia
Dynamic apnea without fins (DNF) Women 182 - Natalia Molchanova 2013-06-27 Belgrade, Serbia

CMAS recognized world records[edit]

As of July 2014, the CMAS recognized world records are:[10]

Discipline Gender Distance [m] Time Name/Country Date Place Status
Constant weight with fins (at sea) Men 97 - Davide Carrera, Italy 2014-06-21 Salina, Italy Waiting approval
Dynamic apnea with fins in Olympic pool (no salty water) Women 237.80 - Ilaria Bonin, Italy 2013-08-07 Kazan, Russia Waiting approval
Static apnea Men - 10:05 Branco Petrovic, Serbia 2012-10-01 Antalya, Turkey Waiting approval
Static apnea Women - 07:30 Veronika Dittes, Austria 2012-10-01 Antalya, Turkey Waiting approval
Jump blue apnea with fins (at sea) Women 168.69 - Ilaria Bonin, Italy 2012-10-31 Kemer, Antalya, Turkey Waiting approval
Jump blue apnea with fins (at sea) Men 185 - Michele Giurgola, Italy 2012-10-31 Kemer, Antalya, Turkey Waiting approval
Jump blue apnea with fins (at sea) Men 185 - Xaier Delpit, France 2012-10-31 Kemer, Antalya, Turkey Waiting approval
Variable weight apnea without fin (at sea) Men 81 - Devrim Cenk Ulusoy, Turkey 2012-09-26 Kas, Antalya, Turkey Waiting approval
Free immersion apnea without fin (at sea) Men 81 - Devrim Cenk Ulusoy, Turkey 2012-09-25 Kas, Antalya, Turkey Waiting approval
Constant weight with fins (at sea) Men 94 - Homer Leuci, Italy 2012-09-15 Soverato, Italy Waiting approval
Variable weight apnea with fin (at sea) Men 131 - Homer Leuci. Italy 2012-09-11 Soverato, Italy Waiting approval
Constant weight with fins (at sea) Women 70 - Şahika Ercümen, Turkey 2011-11-10 Dahab, Egypt Approved
Variable weight apnea without fin (at sea) Women 60 - Şahika Ercümen, Turkey 2011-11-10 Dahab, Egypt Approved
Constant weight with fins (at no salty water) Men 70 - Michele Tomasi, Italy 2011-10-02 Trento, Italy Approved
Constant weight with fins (at sea) Men 87 - Devrim Cenk Ulusoy, Turkey 2011-10-02 Kas/Antalya, Turkey Approved
Free immersion apnea without fin (at sea) Men 80 - Devrim Cenk Ulusoy, Turkey 2011-10-01 Kas/Antalya, Turkey Approved
Constant weight with fins (at sea) Men 86 - Homer Leuci, Italy 2011-09-09 Calabria, Italy Approved
Jump blue apnea with fins (at sea) Men 175.66 - Michele Fucarino, Italy 2011-09-04 Tenerife, Spain Approved
Jump blue apnea with fins (at sea) Women 158.54 - Ilaria Bonin, Italy 2011-09-04 Tenerife/Spain Approved
Static apnea Men - 09:32 Branco Petrovic, Serbia 2011-09-02 Tenerife, Spain Approved
Static apnea Women - 06:38 Sophie Jacquin, France 2011-09-02 Tenerife, Spain Approved
Dynamic apnea with fins in Olympic pool (no salty water) Men 250 - Goran Colak, Croatia 2011-09-01 Tenerife, Spain Approved
Jump blue apnea with fins (at sea) Men 171.45 - Alfredo Roen, Spain 2010-10-10 Tenerife, Spain Approved
Jump blue apnea with fins (at sea) Women 144 - Monica Barbero, Italy 2010-10-10 Tenerife, Spain Approved
Dynamic apnea with fins in Olympic pool (no salty water) Men 248.52 - Goran Colak, Croatia 2010-09-13 Zagreb/Croatia Approved
Dynamic apnea with fins in Olympic pool (no salty water) Women 205.44 - Ilaria Bonin, Italy 2010-06-12 Lignano, Italy Approved
Constant weight with fins (at sea) Men 84 - Homer Leuci, Italy 2009-10-04 Andora, Italy Approved
Constant weight with fins (at sea) Men 83.1 - Devrim Cenk Ulusoy, Turkey 2008-10-26 Antalya, Turkey Approved
Jump blue apnea with fins (at sea) Men 159.54 - Devrim Cenk Ulusoy, Turkey 2008-09-05 Antalya, Turkey Approved
Constant weight with fins (at no salty water) Women 57 - Tanya Streeter, USA 1998-12-28 Ocala, Fl, USA Approved
Constant weight with fins (at sea) Women 67 - Tanya Streeter, USA 1998-09-19 S.Maria Nevernese, Italy Approved
Constant weight with fins (at no salty water) Men 55 - Eric Cherrier, France 1997-08-09 Lac De Sainte Croix Du Verdon Approved

Recreational[edit]

Freediving is also a recreational activity, celebrated as a relaxing, liberating and unique experience significantly different from scuba diving. The advantages freediving has over scuba diving are:

  • less equipment to wear
  • greater mobility and speed
  • lower diving costs
  • shorter preparation time
  • no decompression time for deep dives
  • greater visibility due to a lack of exhaled air bubbles
  • no distracting sounds like regulator breathing
  • greater time in the water since air tank refills are not needed

Experienced freedivers can often go as deep as scuba divers, and sometimes deeper.[clarification needed] Recreational freediving is practiced by many people ranging from the average snorkeler to the professional freediver. Recreational freediving is also frequently practiced in freshwater springs due to excellent visibility and underwater caverns.[citation needed] This type of freediving into spring caverns and caves is very different from diving in the ocean. Even though every spring cave is unique, these are the general differences:

  • A dive light is usually required.
  • The freediver must usually swim laterally to exit the cave before ascending to the surface.
  • The freediver may also pull on large rocks or the cave structure to enter/exit the cave.
  • The freediver must avoid stirring up silt so that visibility is not lost.
  • To conserve energy/oxygen, if possible, the current should be avoided while entering the cave, but it can be used to help exit the cave.
  • If the freediver is penetrating the cave so far that surface light is lost, proper navigation and passage recognition is vital along with a backup dive light.
  • If large air pockets are found inside the cave, they are usually unsafe to breath from.
  • Usually a monofin is impractical to use due to limited space.
  • Some cave passages are so small that shorter fins are better to use than long freediving fins.

Physiology[edit]

The human body has several reflex oxygen-conserving adaptations that manifest under diving conditions. The adaptations include:

  • Reflex bradycardia: Drop in heart rate.
  • Splenic contraction: Releasing red blood cells carrying oxygen.
  • Blood-shift: Blood flow and volume is redistributed towards vital organs by means of a reflex vasoconstriction. Blood vessels distend and become engorged, which in the case of the pulmonary capillaries assists with pressure compensation that comes with increasing diving depth, and without which a largely air-filled chest cavity would simply collapse for lack of compliance.
  • Body-cooling: peripheral vasoconstriction results in cooling of peripheral tissue beds, which lower their oxygen demand in a thermodynamic manner. In addition, Murat et al. (2013) recently discovered that breath-holding results in prompt and substantial brain cooling, just like in diving birds and seals. (Dry) breath-holds result in cooling on the order of about 1°C/minute, but this is likely to be greater with cold water submersion, in proportion to the magnitude and promptness of the dive response.

Techniques[edit]

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.[11] Various athletes attempt to accomplish this in various ways. By and large most divers rely on increasing fitness by increasing lung capacity, by `packing´ and hyperventilating, both of which increase lung oxygen stores.[12] Needless to say, simple breath-holding is highly effective for increasing lung capacity. In addition, training is allocated to enhance blood and muscle oxygen stores, to a limited extent. A substantial proportion of performance is the result of metabolic suppression and redistribution of blood oxygen stores, the so-called dive response. Increasing lung capacity has some draw-backs, however.

Some deep experimental divers, such as Sebastien Murat, model their diving on evolutionary-vetted universal diving strategies employed by diving animal, especially mammals. He dives, almost exclusively, depending on objectives and circumstance on `empty´ lungs or after a passive exhale. This has the effect of greatly accentuating the dive response, which though greatly conserving oxygen stores and redistributing it to more vital organs sacrifices as much as 50% or more of the body's oxygen stores. The analogy is akin to an economical car with a small fuel tank versus a fuel guzzling pick-up truck with a large tank. Another advantage is that it allows skeletal muscles (and possibly heart muscle?) to `learn´ to increase their myoglobin, i.e. locked-in oxygen stores vs convection (hemoglobin) stores, thereby delaying a shift to anaerobic energy stores and, hence, excessive muscle fatigue. Like all things it requires a period of adaptation but can be greatly fast-tracked with an in-depth understanding of the mechanisms involved.

An additional benefit of this technique is that it permits reaching greater levels of hypoxia without excessive respiratory discomfort, due to a build-up of metabolic CO2.Indeed, less overall CO2 is produced since the oxygen stores are much reduced, thereby allowing more frequent reaching of incursion into acute levels of adaptive hypoxia and, hence performance improvements. This would seem to reduce the safety margin before incurring an undeserved loss of consciousness butthis problem can be circumvented to a significant extent because diving on empty lungs substantially lowers metabolic rate and results in a more pronounced brain cooling effect, bot of which offer some little recognized benefits. Specifically, the critical (time-dose) hypoxia tolerance increase the greater the cooling and the lower the metabolic rate, allowing reaching greater levels of hypoxia for longer and without ill effects, i.e., loss of consciousness Murat pers obs.) In non-ballast assisted dives it also minimize the effort of descend to the absolute minimum, since buoyancy is reduced. This helps conserve precious oxygen stores and accentuate the dive response. In addition, the `empty lung´ approach also limits the risk of a reflex reversal of the dive response during ascent, which is triggered by lung re-expansion. This permits swimming and even sprinting with no in-dive penalty. Basically, work effort becomes uncoupled from oxygen consumption, i.e., dynamic times become comparable to static times. This is important because oxygen consumption is normally a function of swimming speed, i.e., hydrodynamic drag scaling effects, but in this instance this approach allows complete `escape´ from drag related effects, i.e., there is no O2 penalty for swimming fast or working hard, and the fundamental drag equation, as it relates to oxygen consumption, becomes meaningless.

To side-step this lung re-expansion reflex problem, something that occur over the last 30 m of ascent, exhale over the last 5 or so meters. Though this may lock-down the dive response, it would require exhaling from depths of at least 20m to completely side-step. Moreover, it cannot avoid the fact that a substantial amount of oxygen is lost by exhaling, and at the worse possible moment, when the diver is already low on oxygen. That apart, buoyancy is lost, which renders this full lung approach somewhat illogical in the first instance. An empty lungs approach offers the additional advantage of substantially lowering nitrogen loads, which in very deep-diving, would otherwise result in nitrogen narcosis, poor decision making ability, potentially, loss of consciousness, and a high probability of decompression illness. Though diving on empty lungs greatly mitigates this problem, instead of doing a safety-stop during the final stages of ascent, Murat goes into pre-descent in-water static breath-hold procedure lasting from 20-50", depending on the stress levels (the greater the pre-dive stress, e.g., the more extreme the dive, the shorter the necessary time to full manifest a pronounced dive response). This early, say, sacrificial strategy of allowing time for a metabolic `shut-down´/lock-down paradoxically does not penalize actual dive time or depth reached but paradoxical substantially enhances performance. Moreover, it reduces nitrogen uptake which has the advantage of `locking-in´ the dive response and reducing metabolism, despite the activity of descent, and greatly limiting nitrogen absorption, especially during the steep (shallow 0-20m) part of the pressure gradient. However, it must be noted that such techniques generally require considerable mental control, physiologic understanding, self-awareness, and pressure adaptation and, beyond depth of about 60 or so meters, the use of sinus and ear cavity-flooding, since there exists essentially no air for pressure compensation of the uppermost airways. Centrally, it requires a high degree of metabolic control to potentiate the dive response; genetic factors and an excessively elevated pre-dive metabolism may limit and negate an individual's ability to fully tap-into such techniques.

Training[edit]

Training for freediving can take many forms and be performed on land.

One example 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, the participant then initiates a walk for as far as they can, until it becomes necessary to breathe again. Athletes can do close to 400 meters in training this way.

This form of training is good for accustoming muscles to work under anaerobic conditions, and for tolerance to CO2 build-up in the circulation. It is also easy to gauge progress, as increasing distance can be measured.

Before competition attempt, freedivers perform preparation sequence, which usually consists of physical stretching, mental exercise and breath exercise. It may include sequention of variable length static apnea, special purging deep breaths, hyperventilation. Result of preparation sequence is slower metabolism, lower heart rate and breath rate, lower level of CO2 in bloodstream[13] and overall mental equilibrium. Failing ordinary warning signals or crossing mental barrier by strong will may lead to shallow water blackout or deep water blackout.[14][15] Trained freedivers are well aware of this and will only dive under strict and first aid competent supervision.[16] However this does not eliminate the risk of deep or shallow water blackout. All safe freedivers have a 'buddy' who accompanies them, observing from within the water at the surface. Due to the nature of the sport, any practice of freediving must include strict adherence to safety measures as an integral part of the activity, and all participants must also be adept in rescue and resuscitation. Without proper training and supervision, freediving/apnea/breath-hold diving is extremely dangerous. The death of Nicholas Mevoli, a diver from New York, highlights the dangers of freediving. He died on 17 November 2013 after completing a dive to a depth of 72 metres.[17]

In fiction[edit]

  • The Pearl by John Steinbeck (1947) is a novel about a poor pearl diver, Kino, who finds the 'Pearl of Heaven', which is exceptionally valuable, changing his life for ever. The novel explores themes of man's nature as well as greed and evil.
  • In Ian Fleming's (1964) James Bond novel You Only Live Twice, the character Kissy Suzuki is an ama diver. This connection was also mentioned in the film version.
  • Man from Atlantis was a 1970s TV series which featured a superhero with the ability to breathe underwater and freedive in his own special way.
  • The Big Blue (1988) is a romantic film about two world-class freedivers, a heavily fictionalized depiction of the rivalry of freedivers Jacques Mayol and Enzo Maiorca.
  • Ocean Men (2001) is a documentary film about the art and science of freediving, featuring two of its most outstanding exponents: Francisco "Pipín" Ferreras and Umberto Pelizzari.
  • In the movie Phoenix Blue (2001), protagonist Rick is a musician who freedives competitively.
  • The children's novel The Dolphins of Laurentum by Caroline Lawrence (2003), which takes place in ancient Rome, describes the applications of freediving (sponge and pearl diving), and its hazards, as one of the principal characters, as well as the main antagonist, try to beat each other to a sunken treasure.
  • The Freediver (2004) is a film about a talented female freediver who is discovered and brought to an island, where she is trained by an ambitious scientist to break a freediving world record currently held by an American woman.
  • In the film Into the Blue (2005) starring Jessica Alba, a group of divers find themselves in deep trouble with a drug lord after they come upon the illicit cargo of a sunken airplane in the Caribbean. Jessica Alba is an accomplished freediver, and did much of the underwater work; some other stunts were performed by Mehgan Heaney-Grier.
  • In Greg Iles' novel Blood Memory (2005), the main character Cat Ferry is an odontologist and a freediver.
  • H2O: Just Add Water Series 3 added a freediver (Will Benjamin played by Luke Mitchell) as a regular. Freediving is featured in some episodes.
  • The Greater Meaning of Water (2010) is an independent film about competitive constant weight freediving, focusing on the 'zen' of freediving.
  • In the Canadian television series Corner Gas, the character Karen Pelly (Tara Spencer-Nairn) competed in static apnea, ranking fifth in Canada with a personal best of over six minutes.
  • In the American television series Baywatch episode The Chamber (Session 2, Episode 17), the character Mitch Buchannon rescues a diver trapped 90 feet below the ocean surface, but almost dies while suffering the effects of decompression sickness; decompression sickness is highly improbable following freediving exposure to this depth.

See also[edit]

References[edit]

  1. ^ Ivanova, Desislava; Nihrizov, Hristo; Zhekov, Orlin (1999). "The Very Beginning". Human Contact With the Underwater World. Think Quest. Retrieved 2009-09-06. 
  2. ^ Sandra Hendrikse and André Merks (12 May 2009). "Diving the Skafandro suit". Diving Heritage. Retrieved 2009-10-16. 
  3. ^ Lundgren, Claus EG; Ferrigno, Massimo (eds). (1985). Physiology of Breath-hold Diving. 31st Undersea and Hyperbaric Medical Society Workshop. UHMS Publication Number 72(WS-BH)4-15-87. Undersea and Hyperbaric Medical Society. Retrieved 2009-04-16. 
  4. ^ Rahn, H.; Yokoyama, T. (1965). Physiology of Breath-Hold Diving and the Ama of Japan.. United States: National Academy of Sciences – National Research Council. p. 369. ISBN 0-309-01341-0. Retrieved 2009-04-16. 
  5. ^ Galili, Ehud; Rosen, Baruch (2008). "Ancient Remotely-Operated Instruments Recovered Under Water off the Israeli Coast". International Journal of Nautical Archaeology (Nautical Archaeology Society) 37 (2): 283–94. doi:10.1111/j.1095-9270.2008.00187.x. 
  6. ^ Frost, FJ (1968). "Scyllias: Diving in Antiquity". Greece and Rome (Second Series) (Cambridge University Press) 15 (2): 180–5. doi:10.1017/S0017383500017435. 
  7. ^ Thucydides (431 BCE). History of the Peloponnesian War. 
  8. ^ a b c d McKie, N (2004). "Freediving in cyberspace.". Journal of the South Pacific Underwater Medicine Society. 34: 101–3. Retrieved 2013-10-05. 
  9. ^ AIDA International. "World Records". Retrieved 2014-07-19. 
  10. ^ Confédération Mondiale des Activités Subaquatiques. "Apnoea Records". Retrieved 2014-07-19. 
  11. ^ Schagatay E (2009). "Predicting performance in competitive apnoea diving. Part I: static apnoea.". Diving Hyperb Med 39 (2): 88–99. PMID 22753202. Retrieved 2013-10-06. 
  12. ^ Simpson, G; Ferns, J; Murat, S (2003). "Pulmonary effects of ‘lung packing’ by buccal pumping in an elite breath-hold diver.". Journal of the South Pacific Underwater Medicine Society 33: 122–126. Retrieved 2013-10-06. 
  13. ^ Neal W. Pollock, Richard D. Vann, Edward D. Thalmann and Claus EG Lundgren. (1997). "Oxygen-Enhanced Breath-hold Diving, Phase I: Hyperventilation and Carbon Dioxide Elimination". In: EJ Maney, Jr and CH Ellis, Jr (Eds.) Diving for Science...1997. Proceedings of the American Academy of Underwater Sciences (17th Annual Scientific Diving Symposium). Retrieved 2009-04-16. 
  14. ^ Lindholm P, Pollock NW, Lundgren CEG (2006). Breath-hold diving. Proceedings of the Undersea and Hyperbaric Medical Society/Divers Alert Network 2006 June 20–21 Workshop.. Durham, NC, United States: Divers Alert Network. ISBN 978-1-930536-36-4. Retrieved 2008-04-30. 
  15. ^ Lundgren, Claus EG; Ferrigno, Massimo (eds). (1985). Physiology of Breath-hold Diving. 31st Undersea and Hyperbaric Medical Society Workshop. UHMS Publication Number 72(WS-BH)4-15-87. Undersea and Hyperbaric Medical Society. Retrieved 2009-04-16. 
  16. ^ Fitz-Clarke, JR (2006). "Adverse events in competitive breath-hold diving.". Undersea Hyperb Med 33 (1): 55–62. PMID 16602257. Retrieved 2013-10-06. 
  17. ^ Skolnick, Adam (November 17, 2013). "A Deep-Water Diver From Brooklyn Dies After Trying for a Record". The New York Times. Retrieved November 30, 2013. 

Further reading[edit]

External links[edit]