Cut watermelon into 1-inch cubes, removing seeds if necessary. Place the cubes in your largest serving bowl.
Slice English cucumbers into quarter-inch pieces. If using regular cucumbers, peel them first and remove the seeds.
Finely chop mint and basil leaves. Slice red onion as thinly as possible (optional: soak the onion slices in ice water for 10 minutes to reduce sharpness).
In a small bowl, whisk together olive oil, lime juice, and honey until emulsified. Season with salt and pepper to taste.
Gently combine watermelon, cucumber, red onion, mint, and basil in your serving bowl. Pour the dressing over the ingredients and toss lightly to coat everything evenly.
Add the crumbled feta last, folding it in gently to prevent it from breaking down too much.
Cover and refrigerate for 30 minutes before serving to allow flavors to meld. Serve chilled with an extra sprinkle of mint and feta on top.