A kid at my high school, who was on the swim team, died from swimming underwater. They did informal competitions to see who could swim the furthest underwater. He was practicing that by himself, and overextended himself, passing out underwater. There were other people in the pool but no one noticed until it was too late.
I'm sure that's not the only case. Between the risk of drowning, and the difficulty for a lifeguard to tell between someone holding their breath underwater vs actually drowning, I'm not surprised a lot of pools have "don't hold your breath underwater" signs.
I'm sure that's not the only case. Between the risk of drowning, and the difficulty for a lifeguard to tell between someone holding their breath underwater vs actually drowning, I'm not surprised a lot of pools have "don't hold your breath underwater" signs.