Stopping the Steamboat

Because of a dense fog, a steamboat had to stop at the mouth of the
river. A passenger demanded to know the cause of the delay.

"Can't see up the river," the harassed captain replied. "Fog's too
thick."

"But I can see the stars overhead," the passenger said.

"Yes," the captain growled, "but unless the engines explode, we're
not going that way."