AQUA PEARL VOICEThe following information may be of semi-spoilers if you have yet read the manga or watched the anime. All of the following information is based off of the manga version of Mermaid Melody Pichi Pichi Pitch unless stated otherwise. If you have not yet started this series, there may be spoilers. Please be aware.
The Aquamarine Pearl is the source of Hanon's power; she needs it to transform into Aquamarine Pearl Voice. Each pearl that the mermaid princesses possess are extremely special. They need the pearls to sing and defeat the bad guys in the series. Using her Aquamarine Pearl, Hanon can transform into Aquamarine Pearl Voice, and use the power of her singing voice as an offensive attack against the evil creatures of the sea. Hanon lost her pearl at Gaito's castle in the scene with Sara, but thankfully Sara's maid, Baya, was kind enough to give Hanon a spare pearl. This is also seen in the beginning with Luchia. Luchia was unable to sing or transform into anything but a mermaid until Kaito gave her the pearl back.
Each pearl is kept in a sea-shell that is the same color as their pearl voice magic. Hanon, being the aqua pearl, has a white and blue shell that holds her pearl. (Look at photo to the right for exact details about the shell)