Prepare the cucumbers: Place the whole cucumbers on a sturdy cutting board. Using the flat side of a large, heavy knife or the base of a heavy pan, firmly and briefly smash the cucumbers along their length until they crack open and flatten slightly. This helps them absorb dressing better.

Chop the smashed cucumbers into bite-sized, irregular pieces (about 1-inch thick). Place the cucumber pieces into a large mixing bowl.

Prepare the vinaigrette: In a small bowl or jar, whisk together the rice vinegar, olive oil, lime juice, sesame oil, honey/maple syrup, salt, and pepper until fully emulsified.

Assemble the salad: Add the cubed watermelon, mint, and cilantro to the bowl with the smashed cucumbers. Pour about three-quarters of the vinaigrette over the mixture.

Gently toss the salad components until everything is lightly coated. Taste and add more dressing if necessary. Fold in the optional crumbled feta cheese.

Serve immediately for the best texture, or chill for up to 30 minutes before serving. Garnish with an extra sprig of mint, if desired.