[Infernal Mass]

Go up the stairs of the building that's across of the boat. Then jump on the roof and walk to the edge as far as your can go facing the boat. Once there the best thing to do is scope the place out for a few.. All the targetrs on the boat have a set path they walk. Once you get their(moving guards) routines down choose a good time to start. Thankfully 8ball is a little slow so you'll be able to clear a path for him fairly easily once you know all the moving targets routines.