Is there a liquid that is thinner than water? I know there are liquids that will float on water (such as oil) but they are still thicker. If you took a swim in a pool of oil, you'd have a hard time moving about. Is there a liquid that is easier to move in than water (while still remaining below vapourization point)? Maybe liquid hydrogen, helium, nitrogen or oxygen, since they're lighter molecules. But anything that isn't super-cooled?