Mermaids' and humans' worlds combine...

Fictional

Mermaids and humans now know about each other's existence, because a mermaid one day, and a human, who was snorkeling, met and had a strong friendship. Mermaids can now turn into humans after mer-high-school, and humans can now turn into mermaids after high school. They can go to Posaia Academy for Humaids and Mermans, and learn to be either mermaids or humans! Once graduated, you can switch forms at your own will! Humans will trade their magnificent legs for a tail, water-breathing, and water-bending powers of the mermaid, and mermaids will trade their astonishing tails, water-breathing and water-bending for the legs of a human! Mermaids learn the ways of the human, and humans learn the ways of the mermaid. This school has especially helped scientists, and now more than 99% of the ocean and its mysteries have been solved, and the world is more knowledgeable than ever! This has also caused pollution to become illegal, and the world is a much better place than before. The school was founded by the mermaid and human that discovered each other's existence. They decided to do some good for the world and made the school, allowing worlds to collide in hopes of saving the ocean and the entire world. The name is a combination of two Greek gods, Poseidon, god of the water, and Gaia, goddess of land. The Mermaid Course, for humans, and the Human Course, for mermaids, allows them each to learn about the other's ways of life, predators and preys, histories, and anything else they may need to know in order to survive.

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Mermaids have the powers of water-bending, water-breathing, and, sure, the tails may count as a power. Potions provide the rest of any sort of "power" anybody may have. For training, you consume some of the mermaid-human transformation potion. Potions will last until they fully pass through the digestive system. Once you graduate, the potion gets injected into your blood, safely becoming a part of your bloodstream. Once it is injected, that is what allows you to transform for the rest of your life. Is is removable, by a safe potion-particle killing liquid. The liquid with the potion particles disappear from the bloodstream within 48 hours.

There is not really any new technology, but just worldwide knowledge of undersea animals has been expanded by 85% (compared to modern-day 10% of the ocean that has been explored.

May be called "Humaidan".