Boil the shrimp, drain and set aside. Slice Green Onions and red onion. Peel the pomelo and break into bite sized chunks. In a measuring cup, mix the sugar and vinegar, set aside. Place pomelo pieces in a bowl, cover with green onion, red onion and shrimp. Pour vinegar/sugar solution over the other ingredients. Toss well and season with sea salt and pepper to taste. Makes 4 servings.