I Pesciolini is a fishmonger, restaurant and bar all rolled into one. The young guys behind the counter will clean and prepare whatever is on sale from among the wide selection of very fresh fish and crustaceans they have on offer. If you are not quite sure how to cook it, just ask them and they will provide you with detailed yet simple instructions.
If you don't feel like cooking they have a good selection of raw and cooked fish dishes which you can either eat on the premises (inside or al fresco at the tables on the pavement) or that you can simply take away. Take a look at their website for further details.
Pesciolni is also a great place for an aperatif - why not try their delicious oysters with a glass of crisp white wine.