In a medium bowl, combine the garlic, lemon juice, oregano (or marjoram), chile (or crushed red pepper) and 2 tbsp. EVOO. Add the shrimp, season with seafood seasoning blend, if using (otherwise, use sea salt and pepper), and turn in the dressing to coat. Roll up each shrimp in a slice of prosciutto. Drizzle or brush a little more EVOO over the shrimp.
Preheat an outdoor grill, indoor grill pan or a large skillet over medium-high heat. Add the shrimp and cook, turning once, until the shrimp are firm and opaque and the prosciutto is crisp, 3 to 4 minutes.
In a bowl, combine the watermelon, tomatoes, onion, cheese, parsley and mint. Dress with the remaining 4 tbsp. EVOO; season with sea salt and pepper. Top each serving of salad with 3 shrimp.