Event organizer William Trubridge identified the man as Nicholas Mevoli, of New York City's Brooklyn borough.
The incident happened around 2 p.m. off the coast of the Bahamas' Long Island, which is about 164 miles (265 kilometers) southeast of the capital of Nassau.
Mevoli's body was brought to shore, where a local doctor pronounced him dead, police said. His body was flown to Nassau, where an autopsy was expected.
Trubridge said Mevoli was trying to break a record for the deepest "Constant No Fins" free dive at the International Free Diving Competition, a nine-day contest that organizers say brought 56 divers from 21 countries. They were competing for a $20,000 prize as they tried to see who could dive the deepest without fins.
The event was canceled after Mevoli's death, Trubridge said.
Mevoli was the current U.S. record holder for "two or three other" free diving contests, Trubridge said.
The Bahamas competition took place at Dean's Blue Hole, which at 663 feet (at 202 meters), is considered the world's deepest underwater sinkhole in seawater.