I've had several waterbeds over the years.
Most recently I had a waveless pillow top mattress. It is very firm and you don't feel any wave action. Sex on this type is similar to a normal mattress.
The single water chamber type mattress I had early on was the one you feel the full wave action on. It was very difficult for us (my wife and I) to have sex on, especially for me being on top. Trying to roll over is difficult because your body is lower as it pushes the water to other areas of the mattress. Trying to kneel is also difficult.
The best part of all the waterbeds I had was the heater. Living in cold climates, it was very comforting getting into a warm bed.