Shallows Mer:

Shallows mer look more “human” and are less likely to appeal to the uncanny valley, but are largely extremely violent and monstrous, even to each other. Shallows are the stuff of nightmares, the real “monsters”, as an evolutionary response to humans encroaching on their territory to capture them for entertainment or scientific purposes. Shallows were once as passive and kind as the Deepsea mer, but they grew meaner, more vicious and deadly as a result of the slaughter of their kind.

Shallows lack ears but have cartilage webbing that extends where they should be along the line of their jaw. They don't hear the way humans do, but instead use a type of sonar. There's additional webbing along the backs of their arms, heavy between their fingers, and a translucent frill that goes down the line of their back/spine. Shallow mer have gills on their neck and along their chest. Their hair, skin, and scales are a plethora of colors with many more shades and variations than humans. Shallow tails are 2-3 times the size of human legs and transition into scales that go halfway up their chest in a gradual reduction. They have what look like a mixture of nipple-less breasts and pecs, but are a left-over from when they used to be human. Instead of pockets of fat, they're an additional type of miniature lungs that allow them to breathe air outside the water for minutes at a time.

The shallows mer are nomadic and don't remember their culture. They only gather in order to breed, wherein they are able to regain a human form if desired (it takes conscious effort and practice to maintain this form). Shallows mer are hermaphroditic because they're endangered and need to be able to breed with any other of their kind when the time comes. They go into a sort "breeding state" when their bodies come to sexual maturity. This allows them to calmly approach other shallows mer without an immediate territorial response.

They meet in the shallow waters of small, forgotten islands, ones that are too tiny to populate humans. Shallows mer generally only meet once with their breeding partner, and once the deed is done, they depart, never to see each other again. The gravid mer is then left to survive their pregnancy the way they have always done — alone. When they birth their children, they stay with the babies until they are able to impart their wisdom of how to survive. They then abandon their children after ten years and leave them to metaphorically sink or swim.

* Please note, I am intentionally using the word "hermaphroditic" because intersex does not accurately describe them. They have fully function male and female sex organs, whereas intersex people are a spectrum of functionality. Thank you!