Gather all ingredients.

Mix buttermilk, water, salt, and pepper in a small bowl. Pour mixture into a flat pan large enough to hold fillets.

Arrange fillets in a single layer in the pan, turning to coat each side. Set aside to marinate.

Combine cornmeal, flour, and seafood seasoning in a 2-gallon resealable plastic bag.

Add fillets to the bag, a few at a time, and tumble gently until evenly coated.

Heat oil in a deep fryer to 365°F (185°C). Fry fillets in hot oil until crisp and golden brown, about 3 minutes. Work in batches to avoid overcrowding, so fillets have room to brown properly.

Drain on paper towels.