Aqua is the Daughter/Reincarnation of Majah. She's of the same species and has a good amount of her mother's powers and spells, but hasn't yet unlocked everything. but she will in due time. Aqua is extremely cheerful and outgoing, she's like an energetic kid, always looking for new friends to hang and play with. she's not kid-like in mindset however, she's quite matured for her age and isn't naive or too innocent (she is still innocent though) she's still learning more about her world and her place in the universe, but there's so much to explore she doesn't want to waste any time, she's extremely excited and looking forward to the next adventure.
I imagine her voice being a younger girls voice, not too young, but more like a young teen, like 12-14 or so.