The truth is many rabbits really enjoy having watermelon as a treat.
Unfortunately, watermelon is very high in sugars, so you should not give your rabbit a large amount, and you should not give it to your rabbit very often.
The dark black seeds in a watermelon cannot be eaten, so make sure you remove them before you give any piece of watermelon to your rabbit.
If you end up giving watermelon to your rabbit, dont give them any big pieces. try to keep them under half an inch. The juice from watermelons can be very sticky, and if they step on the piece, or rub against it, it can matte their hair. In order to clean your rabbit you will need to give it a bath.
You should not give your rabbit more then a square 2 inches buy 2 inches per week. It would be best to give pieces that are approximately half an inch by half an inch at a time so they do not get messy.
Look at this rabbit eating watermelon