if you encounter one, stay calm, point the ship with the wind at max sail if possible, and get out your bow. A few hits will drive it off, you may not kill it (you want to, for the meat) but either way it will behave a lot like a raid enemy at your house where shooting it once makes it turn and leave for good. The karve is fast enough to minimize its ability to get close and make a hit, when it has wind. The raft ... you will probably die if you encounter one in a raft.