Peel and devein the shrimp, leaving the tails on if desired
Pat the shrimp very dry
Lightly score the underside of each shrimp to help them stay straight
Dust the shrimp lightly with cornstarch or flour
Mix cold water, egg, and flour to make a thin tempura batter
Keep the batter cold and mix it gently
Heat oil in a deep pan to about 350°F to 375°F
Dip each shrimp into the batter
Let excess batter drip off
Fry the shrimp in small batches until light golden and crisp
Remove the shrimp and drain on a wire rack or paper towels
Serve immediately with dipping sauce if desired