The Final Enemy is an underwater quest to penetrate the lair of a species of fish-like monstrous humanoids called sahuagin. After identifying the evil creatures, which have massed in force and viciously organized as a threat to the village of Saltmarsh, the player characters have the opportunity to thwart the creatures' plans and ensure the safety of the little town.
The Final Enemy was written by Dave J. Browne with Don Turnbull, with art by Keith Parkinson, and was published by TSR in 1983 as a forty-eight page booklet with an outer folder. It was designed and developed in the United Kingdom, and was intended for characters of 3rd–5th level. The module was the third and final module in the Saltmarsh series, presenting the climactic events in an underwater campaign of three related adventures set in the town of Saltmarsh which began in The Sinister Secret of Saltmarsh and continuned in Danger at Dunwater.