more useless knowledge?

I learned that the difference between a boat and a ship is that boats can come out of the water. Boats can be lifted out, onto shore or onto a ship, or brought on rails. Ships are only out of water in drydock, where the water is drained away from them.

The main exception to this rule is the submarine. Originally, they were small and carried on ships to the point of deployment, and the name stuck. Also, ships confined to the Great Lakes (lakers, or lake boats) are generally referred to as boats.