Take your watermelon half and scoop out a small hole in the center, a few inches wide should be good.

Wrap the watermelon in plastic wrap or put in a container and place it in the freezer. The trick is to freeze it until the watermelon is just frozen. If you freeze for too long it can become too hard. If it’s too hard, just let it sit on the counter until soft enough to scrape.

Pour the heavy cream into the center a little at a time. Using a metal spoon, scrape the cream into the watermelon using long strokes. The cream will slowly thicken and combine with the watermelon until you have ice cream. 

Continue pouring in cream and scraping until you have your desired amount of ice cream. 

Serve immediately. Enjoy!

Also try with frozen cantaloupe or honeydew!