In a large skillet cook mushrooms in hot oil over medium heat about 5 minutes or until tender. In a very large bowl, stir together cooked mushrooms, cooked rice, water chestnuts, celery, onion, and green pepper. Stir in mayonnaise, tomato juice, salt, black pepper, and paprika; mix well. Stir in shrimp and imitation crabmeat.
Spoon seafood mixture into a greased 3-quart rectangular baking dish. Sprinkle almonds over. Bake in a 350 degree F oven for 30 to 35 minutes or until bubbly. Divide hot casserole between bowls and sprinkle with cheese.