is it safe to sleep in Maldives water villa

It's more of a warning to weaker swimmers to take care than something to be very concerned about. The water around Maldives water villa tends to be only waist deep so it's more of a bother if you're actually in the water than upright with your feet in the sand.However if you can't swim then I'm not sure how much time you're going to spend in the water anyway. I'd recommend sticking to the very shallow water by the beach rather than the slighter deeper water around the villa. And of course, don't go anywhere near the water if you're on your own.