Nicholas Mevoli saved money from an assortment of jobs to pay for the bottomless pursuit of holding his breath and sinking his body as far as possible into the ocean.

He practiced holding his breath in bathtubs and Brooklyn swimming pools, even seeing how far he could run with one gulp of oxygen. For roughly the past two years, free diving consumed his life, turning him from novice to national record-holder.

But on Sunday, in pursuit of another record in a championship event in a hidden cove of the Bahamas, in front of the best free divers in the world, Mr. Mevoli came to the surface — but he was not all the way back. After diving down to 68 meters, he paused and reached 72 meters before turning back. After staying under water for 3 minutes 38 seconds, Mr. Mevoli, 32, pulled off his goggles — and quickly fell into unconsciousness. He died soon after.

Mr. Mevoli’s life and death reflect both the spirit of a fast-growing niche sport and its dangers. His rise from novice to record-holder in little more than a year serves both as an inspiration and as a dire warning to an undersea world of divers whose stars rise as the depths they reach plunge.