Deep Ones

Deep Ones are humanoid fish-frogs that live in cities under the sea—though they can also survive just fine on land. They also live forever unless killed.

In the RPG...

Deep Ones stats are mostly the same as a human, which is probably why they are one of the most common monstrous enemies in the game. Their swimming Move speed is higher (for obvious reasons), and their STR and SIZ can get up to 120, but that's it. The only change from the older Malleus Monstrorum to the new is that their attack chance has been raised from 25% to 45%, which makes sense. You'd hope they were better at fighting than a base-level human.

In a video game...

Deep Ones have already made their pixelated debut in Call of Cthulhu: Dark Corners of the Earth, though I'm sure any future Lovecraftian game will feature them as well.

In a film...

Though The Shadow over Innsmouth has already been (loosely) adapted to film in Dagon, I don't actually recall seeing any Deep Ones in it, only Deep One Hybrids. Though I did enjoy Dagon, I'd also like to see a more direct adaptation, including the Deep Ones at the end.