Roped In Trophy
Perform 5 air assassinations from a swinging rope.
There are four ropes on the Jackdaw that you can use to board other ships, one on the back near the helm, one in the front and one on top of each mast.
I found the top ropes to be the easiest to use because you'll land on the deck of the ship where there are more enemies. You should also be tapping before you release the rope.