Heat oil in a large skillet and sauté onions for about 2 minutes.

Add the celery, tomatoes, and water. Bring to a boil. Add the potatoes, olives, capers, pine nuts, raisins, and hot peppers. Season to taste.

Cover and simmer over low heat for 15 minutes, stirring from time to time.

Add the pieces of cod and continue cooking for 10 minutes. If sauce becomes too thick, add a little water while cooking.

Serve very hot.