Use a sharp knife and cutting board to dice the watermelon into small cubes, approximately 1/2-inch in size, and place them in a mixing bowl.
Similarly, dice the cucumber into small, uniform pieces and add to the bowl with the watermelon.
Chop the fresh cilantro finely and sprinkle it over the fruit mixture.
Squeeze the juice of a fresh lime over the mixture, ensuring even coverage. Add hot sauce and a pinch of salt, then toss all ingredients together with a spoon or spatula until well combined.
Allow the salsa to rest for 5 minutes at room temperature to let flavors meld. Taste and adjust salt or hot sauce as desired.
Serve immediately in a bowl or transfer to a serving dish. Garnish with additional cilantro if desired.
