Archimedes' principle: principle that states that a body immersed in a fluid is buoyed up by a force equal to the weight of the displaced fluid. The principle applies to both floating and submerged bodies...
Seriously,It's called the tripple point.The temperature and pressure at which a substance can exist in equilibrium in the liquid, solid, and gaseous states.The triple point of pure water is at 0.01°C...