From publisher blurb:
A 5th Edition Mini-Dungeon for four characters of level 5
Fartide Laboratories jealously guard the trade secrets of their potions, and spent fluids produced by mass potion manufacture remain highly volatile, making disposing of them on land risky. Thus, the mages of Fartide Laboratory decided to build their facility half a mile out to sea, tethered to the shore by a floating causeway, allowing the dangerous compounds to dissolve in the boundless sea.
Unfortunately, the crawling things that lair between the rocks of Fartide developed a taste for arcane waste. They grew. They mutated. Five days, ago, a great storm wrecked the region, flooding the laboratory as its magic protections failed. and one of the mutated things came inside. Nobody has heard from the mages since.