Cut calamari into 1 cm rings and check oysters for sand and bits of shell.
In a 4 litre pot, heat olive oil until smoking. Add onion, peppers and thyme leaves and cook until softened but not brown, about 10 minutes. Add wine and tomato sauce and bring to a boil. Add clams, shrimp and mussels and cover.
Cook 3 to 4 minutes until clams have all opened. Add calamari and cook 2 minutes until opaque. Season with salt and pepper, add oysters and oyster liquid and simmer 2 to 3 minutes until oysters have tightened around outer edges. Divide shellfish over pieces of bread in 4 bowls, pour in broth and serve.