The reason a boat, whatever size, can float on the surface of water is because it is the fluid itself which holds it up. The water offsets the force of gravity which tries to pull everything to the centre of the Earth.

The upward push on a floating object is called ‘buoyant force’ or simply ‘buoyant’. If you want to feel this force just take a blown-up beach ball into the water. You will feel that the water seems to push up on the ball.

When a solid body is placed in a liquid it pushes some of the fluid aside. If the solid is less dense than the fluid, it will float. A boat contains large quantities of air and is less dense than water. It weighs less than the water it pushes aside, so it floats.