Why wood floats on water?

Wood floats on water due to a simple principle of physics called density. Density is the mass of an object divided by its volume. An object will float if it is less dense than the fluid it is placed in. The density of water is about 1 gram per cubic centimeter (g/cm³). Wood, because of its porous structure filled with air pockets, has a density lower than 1 g/cm³. So, even though a log of wood is heavy, it's not heavy for its size. The upward force of the water (buoyancy) pushing on the wood is greater than the downward force of gravity pulling the wood down, causing it to float. It's the same reason a giant steel ship floats—it's shaped to displace a lot of water, reducing its effective density.