Aquaphonis is a minor character that only appears in one episode ("The Silent Siren") as the antagonist. However, she is seen in the theme song, swimming near a slip wreck. We don't know who her husband is.
Aquaphonis is a beautiful, young adult mermaid with long red hair (characteristic to most mermaids visiting Rosemond in the series) and it's mostly tied into locks with blue ribbons holding them in place. She has grey eyes and wears mostly turquoise halter top and arm warmers that start from below the shoulders down to her webbed hands. When she goes on land, her tail becomes legs and she has dark grey pants and brown shoes. In "Boil, Bubble, Toil, and Trouble", she's had boils on her that were passed onto Tara and Sparrow, and is seen wearing a hooded cloak like Loralei's.
In "The Silent Siren", Aquaphonis escapes from Otherworld with her daughter to steal the voice of Madney Speers and another talented singer's voice. Both she and her daughter are mute, and must have a voice to protect themselves from their predator, the Orca, back in Otherworld. Tara enchants her voice to bait Aquaphonis into coming out, but Aquaphonis manages to escape with her voice. Cal later steals back a voice for Tara from Aquaphonis's necklace, but it turns out to be Madney's. In the end, Aquaphonis returns both of the voices to their original owners and is given a voice by Master Chem instead. She and her daughter return to Otherworld and do not come back.