Heat 3" of oil to 350 F in a deep fryer or Dutch oven.
In a pie plate or shallow bowl, combine the flour, paprika, garlic powder, salt, pepper and cayenne.
In another pie plate or shallow bowl, stir together the buttermilk and water.
Place a wire rack over a cookie sheet.
Coat the shrimp in the flour mixture and shake off any excess.
Roll the shrimp in the buttermilk and shake off any excess.
Return the shrimp to the flour mixture and coat again. Shake off any excess and transfer to the wire rack.
Working in batches if needed, fry the shrimp for 1-2 minutes (I prefer 1 minute and 30 seconds), turning once, until golden brown. Remove to another wire rack or a paper towel-lined plate.