We made watermelon rind pickles when I was a kid. Also after I marred. The thick rinds work much better.
As I remember, they were all very very sweet, so I wonder if they could be spiced and sugar reduced for a bit different product.
I also read that watermelon seeds are very nutritious and can be roasted like pumpkinseeds to eat - Well who knew? I was always told not to eat the seeds, or a watermelon might grow in my stomach. What nonsense adults tell kids sometimes.LOL