thanks everybody for your input, this is what I found. for canival .....
Scuba Gear Diving Knives: Diving knives are permitted on board. Due to security reasons, the knife will be confiscated by Shoreside Security at embarkation and turned over to the ship’s Chief Security Officer. The guest will sign for the knife for diving excursions and return it to the Chief Security Officer upon returning to the ship. At the end of the cruise, the knife is returned to the guest in the cruise ship terminal.
Mike