So I have had this idea..
Imagine a crossbow with a rope attached to it. You can shoot it over and hook onto enemy ship's and it'll pull them in for boarding. But you have to keep it in your hands until someone boards the ship and drops anchor and the enemy's can hit the hooks 5 times and pop them off their ship. But I think it'll make for really interesting combat and crews could decide between boarding or shooting the enemy ship. So I think it should be considered.
Grappling hooks
Honestly i would prefer something with a little more skill involved that point and shoot for a grappling hook. maybe a length of rope that has the hook at the end and you have to spin the grappling hook and the longer you spin it the faster it gets until it is at max speed (maybe 6 seconds to max speed?) speed = distance traveled by the hook, with gravity effecting it so you might have to angle it as well to get the right shot. Then you can pull yourself over surfaces using the rope. I'm thinking the theoretical max distance it could go is 25ft. Would be useful for climbing down cliffs, boarding enemy vessels, or even swinging from ship to ship like they do in so many pirate movies.
@curstblackbeard Grappling Hooks would be helpful whether it be to board other ships and reel them in or to help bring your ship into port.
