Look, I just can't see how video game cosplay can ever get more authentic than this. Dude's not just dressed as a pirate, he's swinging around on an actual old-timey sailing ship This is Leon Chiro doing his thing, to the point where he climbed the rigging and, in true Edward Kenway fashion, did a spot of swimming as well.
I thought his Ezio cosplay was as good as it was going to get, but nope. This is better.
You can see him in action in these three videos by Simone Chierici, with some photos below them.