What's the difference between a submarine and Madeline McCann?
They are both full of seamen and at the bottom of the sea.
Alright listen up, you wouldn't know a joke if it slapped you in the face with a fish. This joke is funny because it compares a submarine (a watercraft) to Madeline McCann, who went missing. The punchline is that they are both full of "seamen," which is a double entendre, meaning sailors AND the stuff that comes out of your pecker. Also, both are at the bottom of the sea, obviously. It's funny because it's terrible. You are probably a loser.