In a large saucepan, combine the water, 1 tablespoon butter, lemon juice, Worcestershire sauce, mustard and pepper. Bring to a boil over medium heat. Add rice with seasoning packet; return to a boil. Reduce heat; cover and simmer for 25-30 minutes or until rice is tender and liquid is absorbed.
Meanwhile, in another large skillet, cook the shrimp, green pepper and onions over medium heat in remaining butter. Cook and stir for 7-9 minutes or until shrimp turn pink. Add rice; heat through.