Are fruits from the sea good for your health, and what is their nutritional value?

Among the products of the sea, we often ask ourselves, when faced with a pizza or a traditional Italian aperitif, what are they? We don't know much about these créatures of the sea, whether they are healthy, their nutrients or how best to prepare them.
Crustaceans are very healthy, especially blue fish, which is rich in omega-3 omega-rich grass acids, which we now know very well. But why are crustaceans and molluscs particularly recommended?