"The Deep Ones are creatures in the Cthulhu Mythos of H. P. Lovecraft. The beings first appeared in Lovecraft's novella "The Shadow Over Innsmouth" (1931). The Deep Ones are a race of frog-like, ocean-dwelling creatures with an affinity for mating with humans".
(Source: The Secret Scribes of W'kp'dia)
Or it could just be a rock.