Preheat an outdoor grill to the highest setting. Brush both sides of watermelon with coconut oil. Place on grill and sear both sides just until the grill marks caramelize and turn golden brown. Remove from grill and place on a serving platter. In a small bowl, stir together yogurt, honey, and lime juice. Whisk until smooth. Spoon over the top of each watermelon slice. Sprinkle with salt. Garnish with fresh mint. Enjoy!