Boat Issues-Invisible Wall
Your movement is controlled by the server, but your display is controlled by the client. This lets you run into things you can't see, and prevents you from going into areas you should not have access.
Because of this disjointedness, and because of the general lag of the internet or asset issues in Second Life, it may take objects longer than optimal time to rez. This means that if you're going full-bore through a waterway you'll likely encounter things with your face before you see them with your eyes.