Loos on yachts are scary. You have to pump seawater through them by hand. And then remember to lock the pump or it'll slowly continue to fill with water. And you'll sink. Which way around the switch goes confused me lots yesterday as the previous occupant and left it in the wrong setting. Lucky we didn't sink.
I think on the whole I even prefer airplane loos. You might run the risk of accidently getting sucked right out of the plane, but at least you can't crash it by using it.