Oceanic OC's

Mandachordian's

Endangered: Yes

Mandachordians are the composers of the ocean, and are a dying species. They're ability to adapt and understand the ocean is quicker than others.
Their connections to the ocean is very strong, so much that the ocean responds to their emotions and vitals.

They each wield a song blade that can be used to control the water, and be used to play music. That is because the weapons can turn into actual instruments.

Behavior: most mandachordians are peaceful and shy, but also very curious creatures. They usually afraid of others because of the history of being hunted down.

Habitat: they can live just about anywhere due to being able to adapt so quickly.

Looks:
Their water forms is similar to that a humans, however their hair tend to be literal water as well their clothes. This does change depending on what part of the ocean they are in.
Their actual land form and myth forms changes depending on the person.

Extra:
They are hunted down because they carry valuable resources, and are connected to the Heart of Ocean. 

Their tears which freeze upon leaving their face, are valuable gems and can be sold for a high price.

The song blades

And lastly their connection to the heart of the ocean. They can be used to lead anyone to the heart which is the source of all the music that runs through the currents. The heart itself contains valuable resources that can do just about anything you can of. The amount of resources the heart gives and surrounding the heart is endless.

Known Mandachordians:

Marianna is the only one known, although there are more out there in hiding.