Third grade is starting at the prestigious Trident Academy, and two mermaid best friends are diving right into the deep end. Shelly and Echo are thrilled to be back in the classroom, but navigating the underwater school yard is not going to be easy. They have to deal with Pearl, a wealthy and bossy classmate who loves to show off, and Rocky, the class clown who is always causing a splash. On top of that, their new teacher, the grumpy Mr. Fangtooth, hands out a massive first assignment that threatens to tear the girls' friendship apart. As they struggle to complete their school project, Shelly and Echo must figure out how to work together and handle the social currents of Trident City. This imaginative chapter book introduces a vibrant underwater world filled with relatable school drama. It offers a perfect blend of fantasy, friendship challenges, and fascinating marine facts that will captivate young readers.