Cut fish into 3-4 inch pieces; soak overnight in cold water. Change water several times. Place cod in a saucepan with enough cold water to cover. Bring to boiling point. When cool, remove the skin and bones.
Make a thin batter with flour, water and a little salt. Heat oil in a frying pan till hot enough to brown a 1 inch bread cube in 1 minute. Dip cod into batter and fry quickly until browned on all sides, about 3 to 4 minutes. Cook only 3-4 pieces at a time. Serve piping hot with scorthalia (garlic sauce).