Winter you put memory foam to keep you from the cold water, in summer you sleep on the cold water.
Only downsides to a water bed are: 1. Heavy 2. You have to add chemicals to your mattress as regular maintenance 3. It can't really be extra firm (but a lot more firm than people think)
The water will steal every bit of heat from your body, but you'll stay warm with a blanket
Sometimes I can’t take a bath cause the moving water makes my head spinny. I can’t imagine how bad the water bed would feel lol. I’d probably have mid night breaks for puking.
High-quality water beds have stabilizer pads in the mattress
The idea of the old crappy 70's water bed where they slosh around is a poor idea.
You aren't laying on a ziploc bag barely filled with any water.
It's more like a ziploc bag filled with molasses. If I pushed a corner down it would slowly bring up everywhere else. If I stopped pushing a corner it everything would slowly go back down.
Say I have a massive gut and sleeping on my right side. I'm displacing X amount of water. If I was to turn to my left side I am still displacing the same amount of water. Just the empty space that use to hold my gut would be filled with the water from the other side where my gut is now. Someone on other side of bed wouldn't even feel it because the water underneath them doesn't change.