Aquatos was born in Equantica as an alicorn prince. He was really joyful as a little filly. When he was younger, he wanted to join his parents' royal guards. However, he had other things to do. He was still a prince, but King Barrier Reef decided to help him with that a bit. He showed him how to do 1st-grade magic, and fighting skills. Aquatos soon discovered that he was as good as both a Commander of the Royal Guards and a prince. Then, he got his cutie mark, a magic embled shield with a trident.
When Aquatos grew up years later, he came to see the birth of his newborn sister, Marenia. He and his other sister, Princess Aquatatic, would babysit Marenia while their parents were gone. Years later, Marenia grew up, made new friends, and became a princess. However, things changed when Equantica was cursed during Discord's reign. The entire city was sent under the seas of Destiny Islands.
Years later, the city was invaded by pirates lead by the infamous Captain Taiklar Blackheart, and robbed of many treasures, including the Trident of Benevolence, which kept Equantica's friendship, kindness, and forgiving of land creatures flowing. Aquatos fought the pirates, but his guards were no match for them. He lost his father, and his mother was almost killed. The ship fled when the Purple Sea Dragon Guardian of Equantica attacked. Unfortunately, thanks to Dead Sea, the Purple Sea Dragon was killed, and no one ever knew about it. Not even Aquatos.
After this, Aquatos, Aquatatic, and Marenia were cast with a spell by their mother to keep their kindness and compassion for land creatures flowing. Years later, Dead Sea took away Marenia's wings, and the spell protecting her from the curse. She was soon unsympathetic against land creatures, especially when Geogra comes in and turns them against them. Since then, Aquatos and Aquatatic have been trying to help Marenia any way they can. That is until a certain yellow pegasus pony wishes to see life underwater, and becomes a merpony in exchange for helping them.