Free diving is any of various aquatic activities that share the practice of breath-holding underwater diving. Examples include breathhold spear fishing, free-dive 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 direct assistance of a self-contained underwater breathing apparatus (scuba).

Free-diving 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 free-diving, some sports are more accepted than others. Examples of recognized free-diving activities are (non-) competitive free-diving, (non-) competitive spearfishing, free-diving photography and mermaid shows. Less recognised examples of free-diving include, but are not limited to, synchronised swimming, underwater rugby, underwater hockey, underwater hunting other than spearfishing, and snorkeling. The discussion remains whether free-diving is only a synonym for breath-hold diving or whether it describes a specific group of underwater activities. Free-diving is often strongly associated with competitive breath-hold diving or Competitive Apnea. It is a sport in which competitors attempt to attain great depths, times, or distances on a single breath and without the assistance of breathing apparatus like SCUBA. The following remainder of this article will only discuss competitive free-diving as an athletic sport.

 Competitive free-diving

Competitive free-diving is currently governed by two world associations: AIDA International and CMAS. Most types of competitive free-diving 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 only done 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 with fins. 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’ ("poids constant") refers to the fact that the athlete is not allowed to drop the weights during the dive. Both bi-fins and mono-fin can be used during this discipline (AIDA).
• Constant Weight without fins follows the identical rules as Constant Weight with fins, except no swimming aids such as fins are allowed. This discipline is the youngest discipline within competitive free-diving and is recognised by AIDA International since 2003 (AIDA).
• Free Immersion is the discipline in which the athlete uses the guideline 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 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 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 air-filled bag to return to the surface (AIDA).
• "The Cube" is also known as "Jump Blue" and is a discipline in which an athlete has to descend to 10 meters and swim as far as possible in a cubic form of 15 x 15 meters (CMAS only).

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