Chop the watermelon into cubes. Slice the cucumbers (if using an English cucumber, slice it into half moons). Chop the basil. Zest the lemon.
Arrange the watermelon and cucumbers on a platter in an attractive way.
Sprinkle with feta crumbles, lemon zest, and sea salt. Taste and adjust flavors as desired. (If you’d like, you can add freshly ground black pepper or a drizzle of olive oil.) Serve immediately.
Notes
If making ahead, refrigerate the cubed watermelon separately: it releases a lot of water after it is cut. Then assemble the salad directly before serving.