Why do I always see water being pumped out of a ship's hull? What did they do before water pumps?

On pictures and in video, I always seem to see water flowing back into the sea, or lake, or whatever on large ships. Where does this water come from? Is it leaking through the hull? Was it used to cool the engine? Recently I saw a old, fully rigged ship photo, (wikipedia: ship) and the ship portrays an old ship, I'm sure before mechanical pumps, and there is water out the side. When the tourist ship sank recenlty in Greece, there was water shooting out of the hull in those photos too, but half the ship was under water.