The boat flows smoothly forward.

[Tunnel of Sorrow]
Thickets of brambles, mixed with wild roses line the banks quite solidly. The current swirls the boat around some unseen snag below the surface. The thought of trying to clamber ashore through those formidable thorn banks is not a happy concept. Every rose has a thorn it is said, but those that can be seen, seem to be overachievers.
Obvious exits: none.