Peel and devein shrimp, leaving tails intact; cut a slit almost through back of shrimp, using a paring knife. Open shrimp, and flatten. Bring water to a boil. Add shrimp; cook 1 minute. Drain; place in a shallow pan. Cook onion, green pepper, and celery in 1/4 cup butter in a skillet, stirring often, until tender. Combine crabmeat and next 6 ingredients in a bowl, stirring gently. Stir in vegetable mixture. Top each shrimp with 3 tablespoons crabmeat mixture; sprinkle with paprika. Drizzle 1/4 cup butter over top. Bake, uncovered, at 350 for 20 minutes. Broil 5 1/2 inches from heat (with electric oven door partially opened) 6 minutes, basting twice with pan drippings.
