No-limit apnea is an AIDA International freediving discipline of competitive freediving, also known as competitive apnea, in which the freediver descends and ascends with the method of his or her choice.^[1] Often, a heavy metal bar or "sled" grasped by the diver descends fixed to a line, reaching great depths. The most common ascension assistance is via inflatable lifting bags or vests with inflatable compartments, which surface rapidly. The dives may be performed head-first or feet-first.

This form of diving is considered extremely dangerous by diving professionals.^[2] No-limit apnea has claimed the lives of several divers.^[3][4]

The three main differences between free diving disciplines that involve diving to depth and those that occur at the surface are that you can not interrupt the dive, there are periods where work is performed and the diver is impacted by direct effects of pressure.^[5]

The current no-limit world record holder is Herbert Nitsch with a depth of 214 metres (702 ft) set on 9 June 2007, in Spetses, Greece,^[6] however, in a subsequent dive on 6 June 2012 in Santorini, Greece to break his own record, he went down to 253.2 metres (831 ft) and suffered severe decompression sickness immediately afterwards^[7] and subsequently retired from competitive events.

• Competitive apnea – Underwater diving without breathing apparatus