An adult Nebrian can vary in length (height?) from 4 to 8 feet. Outwardly, they appear as humanoids with large dorsal fins slanted back, and their fingers and toes are connected by a web of skin to allow fast mobility in the water, as well as being able to perform basic tasks using tools. They have a total of six gill slits, three each at either side of the body where humans would have false ribs. They are considered full grown after three years, and have an average lifespan of 35-40 years, which is why rare individuals over 50 years are respected as advisers of the tribe. Their lungs (see below) allow them to breathe on the surface, though they begin to suffer from dehydration after six to eight hours.

Though appearing human at first examination, their bone structure is mostly cartilage, similar to that of most sharks. This similarity with sharks is further deepened by the fact that their skin contains numerical denticles pointing backward. These denticles make Nebrian skin thick and leathery, acting like a protective layer against wounding. In addition, while their skin would feel smooth running one's hand along the direction of the denticles, this same trait gives Nebrian skin sandpaper-like qualities stroking the other way.

Nebrians are carnivorous, having a set of teeth that mostly consists of pointed, serrated teeth that are replaced every year on average. They live off of a diet of fish, though they have been known to attack other prey if the opportunity presents itself. They do however posses an intelligence of around human level, and will generally not attack another life form it perceives as intelligent. They have a tendency to be curious when encountering something new, so travelers are recommended to try and communicate with the Nebrian upon contact. Running away, panicking or emitting similar 'prey-like' behavior is strongly discouraged.

Nebrians have a tongue, and communicate using speech and vocal cords, but due to a heavily descended larynx (situated in the lower respiratory tract) the frequency of their speech is at the lower stage of the audible spectrum. Though this makes them perfectly understandable under water, the lack of high tones might make them hard to understand to a human.