Constant weight bi-fins

Constant weight bi-fins, denoted by the acronym CWTB in competition notation, is a competitive freediving discipline wherein the freediver wears a pair of bi-fins (or stereo, as opposed to a monofin) to descend along the line with or without the use of their arms. Pulling on the rope or changing ballast will result in disqualification; only a single hold of the rope is allowed in order to turn and stop the descent and start the ascent. The diver is prohibited from using a dolphin kick; doing so will result in disqualification of the day's dive.^[1]

For AIDA International officiated freediving competitions, bi-fins was previously included under the umbrella term of constant weight (CWT) in competition. Prior to 2019, competitors wanting to use bi-fins in competition would compete under the category of constant weight alongside those using a monofin. In 2019, AIDA formally separated Constant Weight Apnea with Bi-fins (CWTB) into its own category for competition.^[2][1] Following the rule changes, national record and world record titles could now be earned for the category of CWTB.^[3]

For CMAS officiated freediving competitions, bi-fins has been recognized as a competitive category separate to constant weight (with a monofin), with officiated records for bi-fins starting as early as 2015.^[4]

Current world record holders in CWTB

Men

• Depth: 125 m^[5]
• Person: Alexey Molchanov Russia
• Date: 2024-09-10
• Location: Ajaccio, France, 33rd AIDA Freediving World Championships, 2024

Women

• Depth: 113 m^[6]
• Person: Alessia Zecchini Italy
• Date: 2025
• Location: Moalboal, Philippines, 2023