In a large pan, add the olive oil and onion. Cook over medium heat until softened, about 4 minutes. Add the garlic and cook until fragrant, about 30 seconds. Add the white wine, chicken stock and fish stock and deglaze the pan.
Add the salt, saffron and bay leaf into the cooking liquid. Bring to a boil and reduce the heat to low. Cover and let simmer for 10 minutes.
Place the shrimp and sea bass into the pan and cook for 10 minutes, or until all fish is completely cooked. With about 2 minutes of cook time remaining, add the crab, corn and vinegar. Stir to combine and allow to warm.
Meanwhile, toast the baguette slices until golden. Place the bread into the bowl and ladle the soup on top of the bread. Serve immediately.