It is $7 for 1 trip or $12 for an all-day pass. This is more than just getting from point A to B however. The view you are given as you go is wonderful and really the main reason I took it. I went from Stop 7 to 2 just after sunset and had a wonderful view of the inner harbor. The ride was quick, too quick. The worker on the boat was nice and helpful in showing me the route the boat took - they were running some abbreviated route and not making all their stops that night. Also note that the stop to Ft McHenry closes after 30 Sept so you won't be able to take the taxi over there again until 1 Apr.