Located on a small arm of the Krabi River which leads opposite the main village of Koh Klang island, this portion has been nicknamed the mangrove tunnel as the canopy of the mangroves completely immerses you in the shadow and gives the impression of being in a tunnel.
In general, crossing it is part of a boat tour including at least the Khao Khanab Nam mountains and their caves. More rarely, but I strongly advise you to add it too, the tour also goes to Ko Klang island.