Place the water, ginger ale, soy sauce, sugar, garlic powder and ground ginger in a large bowl and whisk until everything is dissolved.
Add the cod to the marinade and place in the fridge for 1 hour. You might need to weigh the fish down with a plate.
Remove the fish from the marinade and pat try.
Preheat smoker to 180°F. Smoke the cod for 2-3 hours or until the internal temperature reaches 140°F.
Notes
Use wild cod when possible. It is healthier for you and just tastes better. Frozen cod works fine too but just make sure they're thawed before cooking.
Use a mild wood for a subtle smoke flavor like alder, apple or cherry.
Since cod has a mild flavor, don't marinate for much longer than an hour or it will be too salty.