Heat the oil in a large, heavy skillet. Add the onion and garlic and cook until they are tender but not brown. Stir in the cuttlefish or squid and cook over medium heat about 30 minutes, until all the liquid from the cuttlefish or squid has evaporated.
Meanwhile force the tomatoes through a food mill and mix with the juice from the tomatoes and the ink. Set aside.
When the liquid has evaporated in the skillet, stir in the wine and cook until the wine has evaporated and the mixture in the skillet is beginning to color.
Stir in the tomato and ink mixture, add the water, and cook gently another 45 minutes to 1 hour, until the cuttlefish or squid is tender, adding a little more water if necessary during cooking.
Season with salt and pepper.
Prepare the polenta and serve topped with the cuttlefish or squid and its sauce.