In a large bowl, combine cubed watermelon, diced cucumbers, sliced onions, and mint. Set aside.
In a small bowl, whisk together olive oil, lime juice, salt, and pepper.
Drizzle dressing over the watermelon mixture and toss gently to coat.
Sprinkle with feta cheese and serve immediately. Store leftovers in the refrigerator for one day.
Due to the watermelon and cucumbers, the salad may become watery if it sits for too long.If you don’t think you will finish all of the salad in one sitting: only add dressing to the amount you will eat. Store remaining dressing and salad separately in the refrigerator for up to 1 day.