cruise food

Question

dear rabbi, i frequently go on cruises and i prefer not to spend tons of money for kosher programs the ships chef has taken me into the kitchen and offered to make fresh fish without any other ingrediants. the kitchen and knives are spotless and because of allergy concerns no knife used for shellfish can touch other foods. can i eat the fish (does the fact that people eat raw fish as sushi remove the problem of bishul akum)?