To eliminate one step and a few minutes of preparation time, buy precooked shrimp at a seafood market or in the seafood department of your grocery store.
In a Dutch oven, bring water to a boil; add shrimp and cook 3 to 5 minutes, or just until shrimp turn pink. Do not overcook. Drain and rinse with cold water. Peel, devein, and roughly chop shrimp.
Heat oven to 350°. In a medium bowl, gently combine remaining ingredients except English muffins. Split muffins in half and bake 5 minutes. Remove from the oven and spread shrimp mixture on the cut side of each half. Return to the oven and bake 10 to 15 minutes, or until mixture is bubbly and bread is toasted. Serve immediately.