It's summer, and the mermaids have trained their tails off at Hillnook Lake. Prepared for a vacation full of fun (and maybe a little mermaid work) they set off for East Hillnook. But when they arrive... Tourists have horribly littered Starfish Hill. And what's worse, garbage is floating out to sea in droves, where sea turtles are eating it...instead of jellyfish Now, it is up to Monica and a beautiful, but deemed "useless" trident, to save the day. Only problem is, none of the other mermaids believe in her plan Can Monica trust her gut to save the turtles?

Sixteen-year-old Caterina eats seaweed instead of buying school lunch. She rallies shamelessly for the ocean, even using school art and science projects as leverage. At Church, she plays her mandolin and sings every Sunday in the choir loft. And she doesn't know why everyone thinks she's so strange ...But if all of that is not enough to make a girl stick out at monotonous--and landlocked --Hillnook High School, Caterina has a huge secret; one that justifies her weirdness: she is really a mermaid. Like all mermaids do, Caterina attracts the attention of a boy via her singing, though not on...

Every year, a mystical wave brings treasures untold to Starfish Hill at midnight on Christmas Eve Eve...and the mermaids can hardly wait to get there to collect them But this year, an unforseen whiteout prevents the mermaids from going...can they still do something meaningful to ring in the Yule Tide?