The Bubbling Cloister of Bloop-Bloop

From the introduction:

Not too far outside of town, along the coast, where the crags reach out of the sea like fingers grasping from the dark below, a hidden chasm holds a secret. The town is starting to drown in the whispers of Mad Cultists. Hidden in alleyways, just out of sight, they pontificate to the weak-willed and fearful. Several fishermen are missing, believed to have been lost to the crags, but some suspect a darker force is responsible...