National Park Service spokeswoman Christie Vanover says Xavier Fleuranceau of Santaquin, Utah, was with three other people at a depth of 350 feet in the Black Canyon area on Saturday when he ran out of air.
Fleuranceau's dive partner shared a spare air tank as the two began to ascend before Fleuranceau separated from a safety line.
He performed a free ascent without gas while the other divers ascended using normal decompression.
Fleuranceau was found face-down in the water and paramedics declared him dead at 1:46 p.m.
Vanover says Park Service investigators are checking the dive equipment for malfunctions.