Just like my favorite fish men in D&D, the Kuo-Toa. If enough of them believe in a god, it manifests as an entity. The best part is canonically they lean towards inanimate objects to be their god.

“One of the most revered gods of the kuo-toa is Blibdoolpoolp the Sea Mother, who takes the form of a female human with a crayfish head, a crayfish’s claws, and an articulated shell covering her shoulders. Blibdoolpoolp was likely invented by a kuo-toa that improved on a broken human statue by adding the limbs and head of a crustacean. In sudden awe of its handiwork, it then named the resulting form a god.”