In a saucepan combine water, lemon, bay leaves, garlic, salt, and red pepper. Bring to boiling. Reduce heat. Simmer, uncovered, 10 minutes.
Turn heat to high. Add shrimp. Simmer for 1 to 3 minutes or until shrimp turn pink. Drain off liquid and discard lemon and bay leaves. Cool shrimp.
In a small mixer bowl combine vinegar, mustard, horseradish, paprika, salt, pepper, and hot pepper sauce. Slowly add olive or salad oil, beating well with an electric mixer. Stir in green onions and snipped parsley.
In a medium mixing bowl stir together cooked shrimp and oil mixture. Cover and chill for 4 to 24 hours, stirring shrimp occasionally.
Using a slotted spoon, spoon shrimp mixture atop lettuce on a platter. Makes 4 main-dish servings.