They float thanks to the displacement of water and the resulting upward force created by that displacement. Since a boat's density is much lighter than the ocean's density, a little upward force is all it takes to stay floating. Even for the heaviest of ships!

Do boats actually float in water?

All boats can float, but floating is more complex and confusing than it sounds and it's best discussed through a scientific concept called buoyancy, which is the force that causes floating. Any object will either float or sink in water depending on its density (how much a certain volume of it weighs).

Does a boat float or sink?

That is, if an object weighs less than the amount of water it displaces then it floats otherwise it sinks. A boat floats because it displaces water that weighs more than its own weight.