Such marine cats are very rare, and sailors consider them even luckier than normal. No vessel captain would dare part with such a cat. They can be very nasty if threatened, often aiming straight for an opponent's eyes. If the marine cat is being somehow held by its attacker and both of its front claw attacks succeed, it can attack with its back claws that round as well. These rear claws each inflict 1d2 points of damage.
Marine cats leave their vessels only for a brief tour of the docks.
Though they sometimes visit other ships, they never board one that has its own marine cat. This is simply a manner of etiquette. These creatures are never taken by sailors from other ships, because it is very bad luck to steal another ship's marine cat. On the vessel a marine cat can get into any area. Sailors often find their cats up in the rigging, in locked staterooms, or sleeping in the weapons magazines.