"Then suddenly I saw it. With only a slight churning to mark its rise to the surface, the thing slid into view above the dark waters. Vast, Polyphemus-like, and loathsome, it darted like a stupendous monster of nightmares to the monolith, about which it flung its gigantic scaly arms, the while it bowed its hideous head and gave vent to certain measured sounds." - H.P. Lovecraft

This is the description given to the fish-like, humanoid creature of Lovecraft's story, Dagon.

I have done my best to create a creature which can dart through the water, while scaly and nightmarish as described.