Picture two fish in a tank. One turns to the other and says, “Do you know how to drive this thing?”
We consider— why should the fish be able to drive a fish tank?
We resolve the puzzle when ithe punch line points out that the word “tank” has two meanings. The fish are actually in an army tank. Whew—that’s a surprise! I’ll bet we’re both laughting.
Just another element of humor. Sometimes when something doesn’t seem to fit in we’re first puzzled, then relieved to finally understand and laugh at the incongruity. Sure, it’s funny.
AF 5/15

One of the healthiest things you can have up your sleeve is a funny bone !