Once you depart the dock, the trip takes approximately 13 minutes.
There are 2 boats on the route running continuously. There is no schedule, they just load and go and run on a cycle. They are approximately 15 minutes between boats. If you wait longer than that, it means the cycle is messed up for one reason or another, but the good part(if there is one) about that is that when one finally shows up and loads, the other will likely be RIGHT behind it.