Place the water, salt, and 1 tablespoon (15 ml) of the vinegar in a medium saucepan and bring to a boil over high heat.
Add the shrimp and remove 1 minute after the water has returned to a boil.
Remove the shrimp with a slotted spoon and rinse under cold water to stop the cooking.
Repeat this process using the same water with the squid and scallops.
Combine the cooked seafood with the remaining vinegar, tomato, cannellini, fresh herbs, olive oil, and salt to taste in a mixing bowl and toss gently to combine.
Serve at room temperature.
Notes
Notes:
The shrimp should be peeled, deveined, and halved lengthwise
The squid should be cleaned and cut into 1/2-inch (2 cm) pieces
The scallops should be halved horizontally for greater flavour
I usually use parsley but marjoram or basil also work well with this dish.