Makes 3 cups.
1 cup diced watermelon
1 mango, diced
1/2 cup seedless (English) cucumber, diced
1/2 cup ripe tomato, seeded, diced
1 jalapeño pepper, seeds and ribs removed, minced
Juice of 1/2 lime, or more to taste
Kosher salt, to taste
Combine all ingredients in a mixing bowl. Chill until ready to use.