If you’re having trouble finding good quality fish in your area, I know several people who have used Catalina Offshore Products to mail order source their sushi-grade fish. They offer $20 overnight shipping anywhere in the U.S. and their prices are beyond reasonable.

1. Combine the watermelon, pineapple, lime juice, and cilantro in a small bowl and toss gently to combine.
2. Pat excess moisture from the tuna steaks with a paper towel, and rub a few drops of olive or vegetable oil on each side. Season both sides with a pinch of salt and pepper. On a grill over high heat, place the tuna steaks and allow them to remain for 2-3 minutes without moving. Rotate the steaks 180˚ to create crosshatch grill marks and let cook for another minute. Flip the tuna steaks and allow to cook for 2 minutes, then repeat the rotation and allow to cook for another 2-3 minutes for medium-rare. If you desire a more well-done steak, reduce the heat to medium low, lower the grill lid, and allow to cook for another 3-4 minutes or until the tuna is opaque throughout.
3. Allow the tuna to rest for 2-3 minutes before serving. Top with the salsa and serve with a wedge of lime.