1.Heat oil in a large saucepan on medium. Saute onion, fennel and garlic 4 minutes, until soft. Add fish stock, water, passata and bay leaf. Bring to boil. Simmer, covered, 15 minutes.
2.Remove bay leaf. Using a hand blender, blend tomato mixture, until smooth. Strain through a sieve; return to saucepan.
3.Return to medium heat. Season to taste. Add fish. Simmer 2-3 minutes, until fish is cooked. Serve with a grinding of pepper, and toast.