Place butter in a 2 quart casserole. Microwave at high (100%) until melted, 1 minute. Stir in water, parsley, garlic and lemon juice. Add celery and onion. Cover. Microwave at high (100%) until tender crisp, 2 1/2 to 3 minutes. Add mushrooms and shrimp. Cover. Microwave at high (100%) until shrimp are pink, 4 to 5 minutes, stirring twice. Serve over hot rice. Makes 4 servings.