I did some questing in Thousand Needles today. Very early in the quest chain you are asked to fend off an attack by Southsea pirates and get to control a riverboat. After the quest is finished, you get a summonable version of the same boat. It works like a mount, and you can use it anywhere in Thousand Needles. Here are some screenshots:
I think the item is permanent, but it only works in Thousand Needles. When you're piloting it you can continue to cast spells, even while moving. So, it's similar to the camel mounts in Halls of Origination.