Prepare fish and shellfish by cleaning and cutting into bite-size pieces.
Heat oil in a large pot. Fry onions and garlic on medium heat for 5 minutes. Add remaining ingredients, except seafood and bring to a boil.
Reduce heat and cover. Cook one hour.
Add fish and octopus, and cook 20 minutes. Add shellfish and simmer 5 minutes more. Serve hot with crusty bread and crisp salad.