I stopped wondering, I totally dicked down a watermelon, ..., the size of the hole has to be loose, with friction, ..., I believe if you jerk off, that's like every human with a penis, you will fuck a melon with some intensity, the endless moisture triggered an intense fuckening, & will again, why not?, it's better than your hand, it's summertime, big fruit & good weather, outdoors is my suggestion