Heat oil in a deep-fryer to 375 degrees F (190 degrees C).
Whisk flour, cornstarch, and salt in a large bowl. Make a depression in the center of the flour. Stir in the water and egg yolk.
Mix just until moistened; batter will be lumpy. Stir in egg whites.
One at a time, dip shrimp into the batter to coat. Do not batter tails. Carefully place a few shrimp at a time into the hot oil. Fry until golden brown, about 1 1/2 minutes.