Fish people ("nom mova") are one of the three species that form the human genus ("nom"). Roughly said, they have a humanoid shape with two legs, arms, a body with a head, and they stand upright. The unusual features fish people possess can be traced back to their aquatic environment as they originate from the great archipelago. Different as one would think, the majority of fish people live on land.
The body of fish people contain a few quirks special to their species. They possess a whale-like tail at the back of their hips strenghthening their ability to swim underwater. Fings or webs can be found between the fingers and toes of this species, furthering the advantage underwater. However, this tail poses a disadvantage in some terrestrial landscape: Fish people are generally bad at climbing. Since the "natural" way of life of fish people is hunting prey in the open seas, they have developed sharper teeth than their humanoid cousins. This oftentimes leads to mistakes of biting one's own tongue while speaking or eating. Other trivial differences is the lower height compared to the average human as well as their round ears.
Fish people have a wider range of eye shapes and colors. Depending on region, their pupils can either be crescent-like, a horizontal oval, or w-like shape. White-grey, blue and yellow colors are common with a few exotic shades. Special evolutionary developments can ensure the usefullness of their eyes in water. Fish people's hair color is rather similar to humans, ranging from blonde to brown to black.
A peculiar variant of the fish people species has developed in the deep sea. The "deeplings" contain more specialized body features not found on other individuals. Different from their surface-dwelling siblings, "deeplings" are much larger in height, possibly originating from deep sea gigantism. Their tail developed to be fish-like, instead of whale-like, with a vertical approach to it's fin. It's also much larger compared to the average tail of fish people. Similar to many deep sea fish, "deeplings" have antannae at their joints ensuring a greater sense of touch. Due to their thin structure, they can easily be overlooked.
The blood of fish people is blue, stemming from a need to survive in extreme temperatures that can be found in the diverse landscape of the sea. To survive underwater, they additionally developed gills to their lungs. As a way of communicating underwater fish people possess a unique organ capable of producing sound loud enough to be heard underwater. This is why they can speak not only on land, but in the sea as well. Unusual to their genus, fish people don't really have profound sexual dimorphism. Apart from certain key features, secondary sexual characteristics can be quite arbitrary and hardly noticeable depending on the person. This leads other species, like earth people, to consider fish people as androgynous beings. The average lifespan of an individual of this species is about 120 years.
There are also some biological differences found in "deeplings". They have the ability to change their skin pigments, like some species of octopodes, that is used to convey meaning i.e communication and hide from predators. On their backs, minor bioluminescent spots help confuse predators from above, they are able to be controlled by the "deepling" individual.