Sauté onion in butter in saucepan over medium low heat until tender. Add clam juice, water and potatoes.
Simmer until potatoes are tender, about 10 to 12 minutes. Add more water if needed.
Cut seafood and fish into chunks. Add to potato mixture. Heat just enough to cook seafood, about 2 minutes. Stir in cream.
In a small bowl, combine flour with ½ cup water. Mix until smooth, then stir this mixture into the soup. Heat and stir until slightly thickened. Taste, and add salt and pepper as needed for seasoning.
Ladle into bowls. Sprinkle with fresh parsley and thyme.
Notes
Alternately, you can use 2 cups of mixed seafood in place of the specific fish noted in the recipe.