Through the pitch-black night, the captain sees a light dead ahead on a collision course with his ship. He sends a signal: "Change your course 10 degree east."

The light signals back: "Change yours, 10 degrees west."

Angry, the captain sends: "I'm a navy captain! Change your course, sir!"

"I'm a seaman, second class," comes the reply. "Change your course, sir."

Now the captain is furious. "I'm a battleship! I'm not changing course!"

There is one last reply. "I'm a lighthouse. Your call."