Swimming death

So, there is a guy swimmer in Tempe, dead from an accidental swimming death. The article calls him an underwater specialist. I am assuming that's how he died?! I've been telling my friend in FL how dangerous excessive swimming underwater is. His coach has them (masters) doing a whole bunch of it. I have known 2 people who've died from trying to go too far. One of them was a KID on my team back in the 60's who had a heart attack. And I know a well-known former Akron swim coach who passed out and the guards, who thought he was fooling around, didn't go in to get him right way. Please, folks, be careful with what you are doing!