Because, unusually, solid ice is LESS dense than liquid water under standard conditions.
Usually the liquid phase is less dense than the solid phase. It happens that a given quantity of ice occupies more volume than the equivalent mass of water. And we’ve all seen the increase in volume when we make ice cubes in a freezer. Ice will therefore float.
How to remember this? Think Titanic!
Should ice be more buoyant in fresh water or salt water?



