Sorry about the delay, my computer went down for a while. Seems ok now.
Anyway. If the pups injections are up to date it should be ok to walk onto the ferry. Or will it be in a car? I've taken a dog on a ferry before and I would personally recommend something that will restrain the pup properly. A harness would be better than a collar, but I still think a crate, or a basket of some sort would be the best way. The pup might try to 'jump overboard' to play in the big puddle

and you would feel safer if it was properly contained. You will be taking it away from it's mum so it will feel bewildered already, without going on a boat with strangers.
Good luck with your new puppy :)