The general term for humans who escaped the torrent of rebelling machines by going to the ocean floor. They are characterized chiefly by the Battle Dress they wear, which are designed specifically to handle the bottom of the ocean.
The upper part of the suits look like unclothed skin (and has consistency equal to skin) in order to reduce water resistance, while the machines attached to the bottom of the body chiefly looks similar to a fish's body to improve mobility. They also possess musical instruments that besides playing music, have other functions, such as manipulating the ocean's currents and being used as weapons.
It is said they can communicate with each other via ultrasound and thoughts if they can see each other on the horizon, and while the Mermaid go into battle wearing light armor, they are the undisputed masters of fighting in the sea. Since rich amounts of energy and mineral ores can be obtained from the ocean floor, they have been able to reach levels of science and technology that not even land dwellers can boast.