So, I didn't see this happen to anyone else, and I couldn't find why this happens. So I start up a new hardcore world, and I play in it for like an hour an I make my base next to an ocean. I look for a bunch of kelp for food, and then I just DIE!!! The death message was death.fell.accident.water, and I didn't drown or anything because I was in the water for 3 seconds. Now my hardcore world is gone .