Place a Dutch oven over medium-high heat. Add 3 tablespoons olive oil. Add the onions, fennel, carrots and leeks with a large pinch of salt and cook, stirring occasionally, until the vegetables are soft and slightly caramelized, 5 to 8 minutes. Add the water, wine and tomatoes and stir in the olives and orange peel. Season with salt and pepper, reduce the heat to low and simmer for 20 minutes, stirring occasionally.
Increase the heat to medium and add the clams and mussels. Cover the pot and cook for 2 minutes. Season the shrimp and squid with salt and pepper then add them to the pot. Put the lid back on and cook for another 2 minutes. After 2 minutes, stir and continue to cook in 2-minute increments until all the seafood is cooked through and the clams and mussels have opened up, about 4 more minutes. Remove the orange peels and discard.
To serve, ladle into bowls, being sure to get an even mix of seafood. Sprinkle some parsley and mint on top and drizzle with olive oil. Serve immediately with crusty grilled bread! (If you like a little heat add a sprinkle of red pepper flakes.)