@Sturgis,
Really?
Or are you joking?
No way you could drown sleeping on one. Even if it sprung a leak, you would just end up with wet sheets and pajamas.
Back in the day when they were popular I heard ( could be an urban legend, I’ll look it up) that someone was trying to empty one and the mattress sloshed over and trapped him underneath and he suffocated. I remember thinking how horrible that would be.
It never woke me up when someone got in or out of bed. Or if it did it was one of those kinda slightly being conscious. If I was awake an some got in or out, it would just be a gentle rocking. Actually soothing.
The only bad experience I had with a waterbed was when I slept in one where the owner hadn’t bothered with the heating element. Woke up in the middle of the night feeling like I was having hypothermia. That was really awful.
Usually though it’s nice and warm and really really comfortable if it’s filled properly. I would sleep very deeply.