Scoop out the watermelon into 1-2" balls or cubes and add to a large mixing bowl. Thinly slice the onion and chop the cucumber into ½" pieces and add to the bowl. Break apart the mint leaves and add to the bowl with the crumbled feta.
In a small mixing bowl, combine the balsamic vinegar, honey, zest from 1 lime, 2 Tablespoons of lime juice, and salt. Stir to combine. Add in the olive oil and whisk until the olive oil creates an emulsion with the other dressing ingredients and thickens.
Pour over the watermelon salad and toss to combine. Serve & Enjoy!