A great idea for left over watermelon.

Watermelon (cubed or thinly sliced)
Cucumber (peeled and cubed and if you want take the seeds out with a spoon before slicing or cubing)
Cilantro – fresh or dried and season to taste – start small and add as needed
2-3 tbsp rice wine vinegar or lime juice

The quantity of each depends on individual or if you are making it for a group.

Mix ingredients together, add cilantro to taste.