One trick is that ocean fish is safe to eat raw (assuming it has been kept refrigerated/frozen). If you have a cut of salmon or tuna, you can just sear it on the outside and serve it, no need to cook it all the way through (which will make it dry and tough). With saltwater fish, it’s better to err on the side of less cooking.

Shellfish are more tricky, they need to either be raised and handled very carefully to keep them clean, or else cooked correctly. Oysters can be served raw, but you want to really trust the source and the handling.