The Coli-Sea-Um Surprise

Kishiko and Harmonique are back from Wintera. The mermaids have reunited and learned that the secret to color changing fins is being true to yourself. They also learned that a mysterious somebody is behind the disappearing color and light. On top of everything, Riviera and Harmonique still haven't resolved their differences. Will the sisters be able to come together and rock the Coli-Sea-Um and help uncover who's stealing the color and light?