Aqua Regina is the ocean goddess who gives the Mermaid Princesses new songs and upgrades for their gear. However, this is all that she can do alone after expending a great deal of energy thousands of years ago when she killed most of the Panthalassa clan. She is needed to ultimately stop the sea monsters, and the seven pearls have to be gathered to summon her; Gaito seeks to summon her as well, so that he can use her to destroy the world. Aqua Regina later gives bands to the mermaids to upgrade their singing power; as in many magical girl series, this is signified by adding frills and accessories to their dresses. She also upgrades their microphones in the end of season one, before she is finally summoned.
Aqua Regina is kind to all mermaids and were there to talk to the mermaid princesses during their Coming of Age Ceremony. She is also brave and a legend because of her actions when she stopped people from taking over the ocean making it remain peaceful.
Aqua Regina has body length blond hair and blue eyes, strongly resembles Lucia. She wears a light blue crown, blue jewelry with red gems, and a see-through shawl with her big puffy white dress. She always has her staff with her, which has a big blue gem with wings on the top and wrapped with green vines and leaves.