The error depends on loading time. If you have a slower connection, the boat will assume you are loaded and leave; you then fall in the water and zone back into DSH.
This boat docks on the southern edge of the Loping Plains, west of the Bloodmoon Keep. Every 3 minutes or so it sails off to Dragonscale Hills, taking anyone onboard with her. It docks at the southern end of Dragonscale Hills.