At first, there was a pulse, at times faint, at times strong. Within 15 minutes, there was none. The team cut off his wetsuit and began cardiopulmonary resuscitation in earnest. Attempts to revive Mevoli, which included three shots of adrenaline at the scene, continued unsuccessfully for the next 90 minutes.

Mevoli, 32, from Williamsburg, Brooklyn, was a relative newcomer to the sport. When he dived to 100 meters in May, he became the first American to break that barrier unassisted. He used a monofin that day, and completed the feat in 3:45. It is this type of free diving — rather than the variety known as variable weight, which uses a sled to take divers deeper than they could ever get on their own — that has exploded in popularity in recent years. Internationally, free-diving schools are multiplying in destinations as wide-ranging as Hawaii, Egypt, Indonesia, Greece and the Bahamas.

Vertical Blue, considered the Wimbledon of free diving, is an annual event that attracts the sport’s top athletes. It is held in a unique arena: Dean’s Blue Hole, a narrow, 200-meter-deep limestone pit, the deepest of its kind in the world. It is set in a cove backed by cliffs that spill into a turquoise bay. The bay laps the shore of an egg noodle of an island that is 72 miles long, home to 4,000 people and under the tourism radar.

This year, 34 athletes came to compete, representing 16 countries, with 26 national records set in the first six days of a competition that was scheduled to end on Tuesday. Athletes compete in three categories: Constant Weight (in which divers dolphin-kick to depth wearing a monofin), Free Immersion (in which athletes pull themselves along a rope down to depth and back to the surface again without wearing fins); and the most difficult event, the one that Mevoli attempted Sunday, Constant Weight Without Fins (where competitors dive without fins at all).

Mevoli began his competitive free-diving career early last year. He won the title at Deja Blue, a similar competition held that year in the Cayman Islands. He won it again this year in Curaçao, finished third at the Caribbean Cup (an event won by William Trubridge, a New Zealander who owns Vertical Blue) in Roatán, Honduras, and took bronze in Constant Weight Without Fins at the world championships in Greece this September.

After his record-breaking spring and meteoric rise, Mevoli arrived in the Bahamas confident and aiming to break another national record, this one in the category of Free Immersion. His attempt to reach 96 meters on Friday went awry, however, when he turned at 80 meters and had to be assisted to the surface. He breached with blood dripping from his mouth. Furious, he screamed and cursed, certain he had blown out his left eardrum, an injury that would end his competition.