The Blood Reef of Morgra

The water along the coast turns red, nets come up empty, and the fishermen no longer return. The beacons along the cliffs now burn day and night, but they hold back nothing of what rises from the deep. The villages send for help, and that help is you.

Beneath the waves, on the Bloedrif of Morgra, a reef of bone and blood coral, the Tide Priestess of the sea devils calls upon her shark god. With every sacrifice, every drowned crewman, her army grows and the tide turns fouler. What she truly means to breed already slumbers in the darkness behind her altar, and it is hungry.

You arrange a way to breathe underwater, explore wrecks and undersea caves, forge a shaky alliance with a school of frightened sea folk, and dive toward the reef while scaled hunters strike from every crevice. Along the way you find the sunken ship whose cargo set the whole cult of the Tide Priestess in motion.

The twist: the shark god is no god but a colossal, half-awakened primordial beast that the Tide Priestess believes she commands but long ago stopped controlling. The climax falls at the blood altar: kill the priestess before she completes the ritual, or turn her own god against her, while the water goes black with teeth and the time until the flood runs out.