Prepare the Fish: Pat the fish dry with paper towel and check over your fish for any bones. If you have a thicker part and thinner part of the fish, cut the thin part off as we will cook this separately to avoid overcooking.
Season the fish with salt and pepper.
Lightly coat each fillet with flour.
Heat oil in a deep fryer or heavy pot to 350F (175C).
Make the Batter: In a large bowl, whisk together flour, baking powder, milk, olive oil, water, salt, pepper, and beer. Don't worry if there are lumps in the batter, this is good.
Fry the Fish: Dip fish into the prepared batter, allowing excess to drip off. Carefully place the fish into the hot oil and fry for 4-6 minutes, or until golden brown and cooked through.
Transfer to wire rack to drain.
Serve: Serve the crispy fish alongside hot chips or sweet potatoes. Garnish with lemon wedges, dill, and your favorite condiments.