1. In a pot, bring water to boil.
2. Chop the potatoes. Thinly slice celery and carrots. Finely chop onion.
3. Add potatoes and carrots to the water and bring back to boil. Reduce heat and simmer, covered, about 10 minutes.
4. In a skillet, heat olive oil. Saute celery and onion for about 7 minutes. Add to the pot.
5. Chop fish and mince garlic, add to the soup.
6. Add parsley, bay leaf and lemon juice. Season with salt and pepper to taste. Cook for another 7 minutes, or until fish is fully cooked.
7. Serve with toasted bread.