Wasn’t there a woman who died doing this a few months ago?
Probably, people die from this fairly regularly.
There have been a number of extreme free divers who have died doing this. One of the more famous was a French free diver by the name of Loic Leferme. At one time he held the world record at over 560 feet. IIRC, the world record is now over 600 feet with an ascent bag. In a pure freedive, I believe it’s in the vicinity of 400 feet. The physiological changes that the body undergoes at that depth are, to say the least, amazing...think pulse of 15-20 bpm, for starters, along with vascoconstriction pulling blood away from the arms, legs, and brain.