Mermaids Shelly and Echo are excited to begin third grade at the prestigious Trident Academy, but snooty Pearl, jokester Rocky, brilliant Kiki, grumpy Mr. Fangtooth, and an argument over their first project challenge the best friends.
While preparing for a unit on storytelling, the mermaids of Trident Academy learn of a legendary pirate treasure in their own city and Pearl decides to find it, despite a warning that it is guarded by a ghost.
Experiencing occasional visions of the future, mermaid Kiki Coral receives a psychic warning that her classmate, Rocky Ridge, will have a dangerous encounter with a giant leatherback turtle, a premonition she fears nobody will believe.
Mermaid Echo is doing tail flips because she's going to see her favorite under-the-sea band, the Rays. They're performing for Pearl's birthday party and everyone at Trident Academy is invited except Echo's best friend Shelly.
