Q: What do you call a wet fruit? 
A: A watermelon!

Explanation:  “Wet” is something that is liquid or has liquid on or in it.  For example, a towel gets wet when you use it to soak up water; the street gets wet when it rains.  Water is wet because it is a liquid.  A watermelon isn’t really wet on the outside (unless it has been rained on or washed) but it does have lots of liquid on the inside. So a wet fruit, is a watermelon.  Mmmm!

Soon it will be summer here in the north and the watermelon will start growing again.  I can’t wait!

Thanks “Tree” for sending the joke.