Freediving is any of various aquatic activities that share the practice of breath-hold underwater diving. Examples include breathhold spear fishing, freedive photography, apnea competitions and, to a degree, snorkeling. The activity that garners the most public attention is competitive apnea, an extreme sport, in which competitors attempt to attain great depths, times or distances on a single breath without the assistance of self-contained underwater breathing apparatus (scuba).

Freediving is a technique used with various aquatic activities. While in general all aquatic activities that include breath-hold diving might be classified as a part of freediving, some sports are more accepted than others. 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 Apnea. 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 sport, celebrated as a relaxing, liberating, and unique experience. Many snorkelers may technically be freediving if they perform any sort of breath hold diving - it is important to stress the importance of training and supervision when making this association.

Like other water sports, freediving is associated with therapeutic properties. The experience of freedom in an underwater environment makes free-diving somewhat of a personal and spiritual journey for many. Yoga is used by many practitioners to increase focus, breath, and overall performance. The 'art' of freediving and the waterpractice outside the athletic and competitive sphere goes beyond the scope of this article.

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 pulse 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 diving, performance-oriented freedivers hyperventilate to a certain degree, resulting in a lower level of CO₂ in their lungs and bloodstream. This postpones the start of stimulation to the breathing centre of the brain, and thus delays the warning signals of running out of air. As the oxygen level of the blood is not increased by hyperventilation, this is very dangerous and may contribute to shallow water blackout and 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, of itself, 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, safety is an integral part of free-diving, requiring participants to be adept in rescue and resuscitation. Without proper training and supervision, free-diving/apnea/breath-hold diving is extremely dangerous.

History

Archaeologists said that people have been earning their sustenance from freediving since the 5th century BCE. The first nation which was famous for it was the haenyeo in Korea. They collected shells and sponges to sell to others. The Ama Divers from Japan began to collect pearls 2000 years ago. But also the spearfishers around the Mediterranean Sea were important for the historical background for the movement of the apnea sport.

Credits http://en.wikipedia.org/wiki/Free-diving

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