1. Thoroughly mix the flour, seasoning salt, garlic powder, and pepper; set 1 cup aside.
2. In a mixing bowl, combine remaining flour mixture, Guinness and water.
3. Whisk until lumps are gone and batter is smooth.
4. Dredge fish fillets in the reserved flour mixture coating well and then dip into beer batter.
5. For best results, cook fish in grease that is heated to 350 degrees.