"Even when they share different habitats, Merpeople still share a lot of similarities, mostly about how the body is built. they have to be strong. They have to be hydrodynamic as much as possible."

The basic physiological aspects of the Merfolks are:

-The Dorsal fin. On the back of the torso, the dorsal fin helps them to switch direction faster with more efficacy, wether its to hunt or escape.
-The Pectoral fins. Located near the waist line or directly on the hips, the pectoral fins are mostly used to maintain a position when they float. For an example, when two of them speak and avoid drifting away. The are fold against the body during the swim to avoid slowing down.
-The Anal fin. Right under the tail near the end, is the anal fin. Like the dorsal fin, its help to take directions.
-The Caudal fin. Used for propulsion, but also to fight during mating seasons.

-Torsal gills. Mostly seen on the Salt water specimens, they act like classical fish gills, located where the rib cage is.
-Pilo-gills. Or know as hair gills. They hare and and facial hairs that filters the oxygen from the water and send it to the brain faster then Torsal gills.
-Neck gills. This can bee seen in both salt water and sweet water specimens. They are located on the sides of the neck and act as classical fish gills.
-Classic lungs. All Merpeoples posses a pair of human lungs so they can breath out of the water.
-Webbed fingers. They are useful for slower swimming.

"Something I could see from my many observations is the muscles mass of these creatures. The have strong arms, abdominal and pectoral muscles. the males especially are all ferociously builded. In fact, I haven't seen one who was not builded like a greek god. But could this slow them during swimming? I am afraid I will not have my answer to this question."

If there is a thing to memorize about the merfolks that is very important is that they are sensitive to heat. In fact, if they stay too long out of the water and exposed to much to sunlight, they will dry, causing ther scales to loose their beauty and gleam and can also cause death by severe dehydration. For that reason, merpeoples tend to stay under the water sruface most of the time and will come out when the sun is covered.

Aging:

Merfolks, unlike muggles and wizards, can live up to 200 years old. Their metabolism is strong and slow, so they do not age as fast as us. For this reason, they sometime skip mating seasons in a row so the population does not overgrow and get out of control.