Q: What is the best way to communicate with a fish?
A: Drop it a line!
Explanation: When you go fishing you drop a line in the water to catch a fish. To “drop someone a line” means to send a short letter, send a note. I suppose now it could even mean to send someone a text message (I never did learn the difference between a text message and an SMS).
This joke plays on the double meaning of “drop a line.”
If you have a joke that you would like explained, well, drop me a line!