Western Channel is a dungeon-like watery passageway that connects the Ancient Waterway to the Western Flow Control platform in Act II of Diablo III.
This zone is modified from its campaign version in Adventure Mode, being more like a typical dungeon - it has two levels, and its exit to the Western Flow Control (which is no longer accessible in Adventure Mode) is replaced by a standard dungeon return obelisk that takes heroes back to the entrance, which remains in the Ancient Waterway. A bounty is sometimes offered to clear all the monsters in the Western Channel's second level.