Atlanteans are an aquatic species with the lower half of their body being similar to that of a shark's tail, and the upper body humanoid in appearance. They have a long tail instead of legs. There are slight differences between the genders, and the gender distribution is roughly 65% female and 35%, male. This combined with females tending to be the more intelligent gender means that workers such as doctors, scientists and engineers are usually female whereas manual jobs such as builders as well as warriors are male. Female Atlanteans have four arms, each with a webbed hand. They have a round head with a large fin protruding out the back that can be of various colours. They have large eyes without eyelids, a small lipless mouth and small nostril holes in their flat, noseless face.

Male Atlanteans are similar to females but have only two arms, are shorter in length and have larger muscles.

Atlanteans are large creatures, being twice the length of a human, most of this being due to their tail.

Atlanteans are not mammals so lay eggs, as a result, they have no nipples. They reproduce via external fertilization meaning that females will lay a few eggs and the male will release sperm to fertilise them. They can however experience sexual pleasure via contact with their private parts.

Atlanteans communicate either vocally through clicks and whistles, similar to whales though more musical, or they communicate telepathically.

Atlanteans are scaleless, hairless, and lack hair on their head or body at all. Their skin colour varies, as do the patterns on it, but the most common colours are blues and greens.

Atlanteans are omnivorous and mostly consume fish and seaweed dishes.

Blue is a female Atlantean born in the capital. Her body is slightly off-white, with her underbelly being pure white. The fins on her head are a pale blue, as is the webbing on her hands, while her eyes are a vivid blue. She is an anthropologist, considered one of the greatest in her field and works as a professor at one of the top universities in the country. She is a kind, gentle and patient person, very inquisitive, and always eager to learn. She lives alone, unmarried in a flat in the city centre, and does not have a partner, or any children.

An ancient, sprawling empire, Atlantis is led by its queen who resides in the royal palace of the capital called Atlantis. The government is led by her and a council of chosen representatives. They are currently at war with the Deep Ones.