Cut the watermelon into 1-inch cubes, removing any seeds if necessary.
Cut the English cucumber into 1/2-inch cubes. If desired, pat dry with a paper towel to remove excess moisture.
Crumble the block of feta cheese into rough chunks using your hands.
In a large mixing bowl, gently combine the watermelon cubes, cucumber cubes, and about three-quarters of the crumbled feta.
In a small bowl, whisk together the fresh lime juice, olive oil, sea salt, and black pepper until well combined.
Pour the dressing over the watermelon and cucumber mixture in the large bowl.
Using a large spoon or your hands, gently toss everything together until evenly coated.
Just before serving, tear the fresh mint leaves by hand and fold them gently into the salad.
Transfer the salad to a serving bowl or individual plates.
Top with the remaining crumbled feta and an extra grind of black pepper if desired.
