Sighs at lack of elementry physics, wood is generally less dense than bricks that’s why it floats, some woods do not float.
When something like a log of wood is put into water, it pushes down on the water and the water moves aside to make room for the object. When there is enough water to push back up against the object with the same force as the object is pushing down, then the object will float!
That’s why a piece of wood that is lightweight for its size will float in a big body of water, like the ocean or a river. However, that same piece of wood might not float in a different smaller body of water.