This is a clone that should be pretty close to the fish you get at Captain D's. I listed two optional ingredients because I ran across a recipe very similar except with a little spice added. Captains D's fish is basically a variation of Fish n Chips, so this probably something you can tweak and perfect by watching videos of fish n chips being prepared.
Note: I have spoken to some and they've suggested that maybe Captain D's uses Cod. I've tried Cod and the meat just did not taste like the Captain D's in my area, so experiment with Cod, Pollock, Haddock, etc and see what works for you. Also, make sure your fish is dry. You don't want to try to make this with wet and water-logged fish. Pat it dry with a paper towel. I've known some to then rest the fish in the fridge or counter top to allow to fish to dry out some. Not using fresh fish can give you even more trouble.