Begin by selecting a ripe watermelon. Slice it in half, remove the seeds, and cut the flesh into bite-sized cubes. Place them in a large mixing bowl.
Prepare the cucumber by peeling it if desired, slicing it in half lengthwise, removing the seeds, and chopping it into small pieces. Add to the bowl with watermelon.
Crumble the feta cheese and add it to the mixing bowl, ensuring it's evenly distributed.
Finely chop the fresh mint leaves and sprinkle them over the salad.
Squeeze the juice of one lime into the bowl and drizzle with olive oil. Season with salt and pepper.
Gently toss all ingredients together, being careful not to break the watermelon cubes.
Let the salad sit for about 10 minutes at room temperature to allow flavors to meld.
Give the salad a final gentle toss before serving. Transfer to a serving bowl or individual plates.
Notes
This salad is best enjoyed fresh, but can be prepared a few hours in advance. Store leftovers in an airtight container for up to two days.