I play a lot of open crews with newer and experienced players and i noticed that almost everyone of them didn't know how to get the Kraken off of the ship. I didn't think it was that uncommon knowledge but ill quickly explain it here for anyone that already doesn't know.
If you want to get the Kraken off of your ship, do not attack the tentacle that has wrapped your ship. What you should do, is attack the head of that tentacle. The head will usually spawn on the left or right side of the ship and will have its mouth open. It will be quite close to the ship and it will be a little shorter the the other tentacles as it is extended around your ship. After you shoot it a few times with your gun or with a cannonball it will retreat back into the water and it will show up on the other side of the ship (sometimes it shows up on the same side). it will do this a few times before letting go of your ship, if you do this efficiently it should get off your ship in under a minute. Sometimes it will lay its head on the ship which you can proceed to hit it with your sword. The reason people get confused is because if you leave the Kraken on your ship, it will eventually get off anyway but if you attack the head, it will get off a lot faster