Cut watermelon half in half lengthwise. Cut each watermelon quarter into triangles. Cut each triangle in half.
Stick the sharp end of a skewer into each watermelon triangle, then place in a glass baking dish. Pour tequila over watermelon, then turn watermelon a couple times to coat. Cover with plastic wrap and place in refrigerator overnight.
Two hours before serving, drain excess tequila from baking dish, and transfer to freezer. When ready to serve, sprinkle with lime zest, mint, and sea salt. Eat!