Yes, they have a pantoon boat that runs back and forth to the Marketplace/Pleasure Island. I believe the last boat picks up around 9:30pm. If your past 9:30 you can use the buss's to get you back.
It's a very nice boat ride. You go by the Disney Institute and the whole ride takes about 15 minutes. I think they are sceduled to leave every 20 minutes.?
Note that the boat does have limited seating, about a dozen people if I recall. During busy times a line will form so you might not get the next boat. Keep this in mind.
If it is a busy time and the boat is crowded, you can also take the walking path from behind DD to the Southpoint area of OKW. It takes about 10 minutes.