Niko

-can swim very well

-can breathe air and water

-his call sounds similar to a newborn kitten's 

-he makes many different sounds! they include squeaking, yapping, trilling, crying, cooing, hissing, and purring. He can also get pretty loud when producing these noises, depending on how excited he is. 

-has a sweet heart and only wants to make others happy 

-is canonically a bit larger than the average adult human. This is the normal size for babies of his species. In a side story where Niko has a human owner, his size is changed so he is just small enough to lay in one's palm.

-has two fingers and 4 stubby ears. 

-The four ears on his head help him sense vibrations, scent particles, changes in the water current, and even the type and number of enzymes inside one's body. Being so, he has a number of tiny organs in his head region specialized to help with said functions.

-has a small birthmark on his left collar

-since he is male, his colors will brighten as he gets older

-has only his four canine teeth. The rest don't come in until 4 months old.

-grows very fast

-has strong durable bones, so they don't break easily. However his skin is soft and smooth so it can get scratched easily. In a side story, his owner knits a sock for his tail, along with tiny mittens to protect his teeny paws

-has invisible fuzz all over him. This is important in cold waters in case his mother isn't there to keep him warm. the fuzz peaks around 3 months old and goes away at 4 months 

-has gills located on his neck and waist. they are invisible at some angles.

-his body is very flexible and squishy

-can see well in the darkest waters and withstand the pressures of the ocean floor

-cries loudly when he is not given attention

-tends to curl up and sleep in warm places where he feels safe

-he uses his tail to express his feelings often. he thumps his tail when angry, vibrates his tail when comfy, and wags/flaps his tail when excited.

-can whip his tail as a defense mechanism. He puts all of his weight and power into this move. It can be used to either strike an enemy or to kick up sand as a distraction. However, this, along with all other defensive behaviors, isn't learned until 3 months old.

-when he feels threatened, he stands on his tail and arches his back in an effort to appear larger, like a cat does

-when he is able to eat solid foods, he has a mostly plant-based diet. On some occasions, he eats fish.

-likes sugar but can only have a tiny bit of it, or else ...

-has very keen senses and can naturally sense many things that humans cannot, such as predicting an earthquake or detecting an emotional/physical imbalance in any living thing. 

-his ears also tell him which directions are north and south by allowing him to sense the Earth's magnetic field. This ability is called magnetoreception. 

-there is an age-old myth that his species is able to grow legs, but must learn how to. Niko proves this myth when he suddenly sprouts two legs from his waist, slightly longer than his arms, and runs on the beach. Each foot has three toes and thumbs and are built ideally for jumping and leaping. They have small claws on them so he is able to push off with more friction. To grow these legs, Niko must stay healthy- meaning that he must be breathing clean salt water often, clean air, and have a well-balanced diet. After use of these legs for several hours, he must rest and eat a large amount of food to regain his energy.

-A fact unknown even to him, Niko has venomous bile. Bile is a digestive fluid found in most mammals, crucial in helping break down waste. He's able to spray it either from his mouth or butt, and it promptly paralyzes animals on contact. This makes his excrement, vomit, and urine slightly toxic to handle as it can cause rashes and irritation on human skin, accompanied by the smell of ammonia. Niko's skin is immune to such toxins, but if exposed to them for a prolonged amount of time, he'll show signs of illness and difficulty breathing.