Grilled Watermelon and Prawns

Name: Grilled Watermelon and Prawns
Ingredients: 2 cups water; 1 cup granulated sugar; 2 red bell peppers, cored, seeded, and chopped; 2 jalapeno peppers, seeded and chopped; 1 clove garlic, crushed; 3 cilantro sprigs, chopped; 1 pound (16 to 20 count) prawns, peeled and deveined, with the tail left on; 1/4 cup olive oil; 2 limes, halved; 1/2 teaspoon cayenne pepper; 2 teaspoons chili powder; 2 teaspoons salt; 1 teaspoon black pepper; 1 small seedless watermelon, sliced into 1/4-inch wedges, rind on; Unsweetened coconut, toasted for garnish; 1 scallion, sliced for garnish