[Exoxus]

Yup. I've gotten onto two Navy Vanguards. After you grapple, walk as far as you can towards the other ship (it should stop you when you are on the railing) then click Control when it says Press Control to board enemy ship. Then it'll do a swinging on a rope animation and you'll be on it. Just do the same thing, but towards your ship to get back.

Be warned! It is extremely buggy when you have boarded another ship! By far the most glitchy place in-game. You could easily fall into the ship, go flying, turn pitch black, or any bug you've encountered in regular places. Once when I boarded, Navy Sergeants kept respawning very quickly, and they all came after me. ._.

-X