I'm actually surprised that this doesn't happen more often. I used to be a lifeguard and I can tell you that people way underestimate the water and how exertive swimming is, especially in ocean/sea water where you also have ever changing currents involved. I think these days with social media sites like this, word just gets around more.
There are so many factors that can go into something like this, and to be honest, it could happen to any of us at any time. You just never know what strange occurrences you can encounter when in nature like this.
And to the post about inappropriate comments, were they deleted or something? I sure didn't see anything inappropriate.