​

​

Overview
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, synchronised swimming, underwater rugby, underwater hockey, underwater hunting other than spearfishing, 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. Freediving is often strongly associated with competitive breath-hold diving or Competitive apnoea. The remainder of this article will discuss only competitive freediving as an athletic sport.



Competitive freediving
Competitive freediving is currently governed by two world associations: AIDA International (International Association for Development of Apnea) 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
    Static Apnea is timed breath holding and is usually attempted in a pool (AIDA).
    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).
    Dynamic Apnea Without Fins- This is underwater swimming in a pool for distance without any swimming aids like fins (AIDA).

Depth disciplines
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 International 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.
Recreational

Freediving is also a recreational activity, celebrated as a relaxing, liberating, and unique experience. Many snorkelers freedive, letting the snorkel flood when they duck below the surface.
Physiology of freediving
The human body has several adaptations under diving conditions, which stem from the mammalian diving reflex. These adaptations enable the human body to endure depth and lack of oxygen far beyond what would be possible without the reflex.

The adaptations made by the human body while underwater and at high pressure include:
    Reflex bradycardia: Drop in heart rate.
    Vasoconstriction: Blood vessels shrink. Blood stream directed away from limbs for the benefit of heart, lungs and brain.
    Splenic contraction: Releasing red blood cells carrying oxygen.
    Blood shift: Blood plasma fills up blood vessels in the lung and reduces residual volume. Without this adaptation, the human lung would shrink and wrap into its walls, causing permanent damage, at depths greater than 30 meters.

Training
Training for freediving can take many forms and be done on the 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 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. Trained freedivers are well aware of this and will only dive under strict and first aid competent supervision. 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.
​
History
Main articles: Sponge diving and Ancient divers
Archaeological evidence suggests that people have been freediving since the 5th century BCE. The first known were the haenyeo in Korea who collected shells and sponges to sell to others. The Ama Divers from Japan began to collect pearls 2,000 years ago.Both Plato and Homer mention the sponge as being used for bathing in ancient Greece and this may represent an early reference to commercial freediving to obtain them; the island of Kalymnos was a main centre of diving for sponges. By using weights 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 long as 5 minutes to collect sponges.
 

Spearfishing around the Mediterranean Sea was important for the historical background for the movement of the apnea sport.