Pestering the queen into sending messages in bottles to the fabled Seapony kingdoms is just one of the many perks to having royal besties, which is exactly what Izzy has been doing ever since first reading about mythical Seaponies in Sunny's old history book. So when Queen Haven hears back from the Queen of the Sparkling Seas, Izzy is eager to dive into the adventure of a lifetime. Pipp, on the other hoof, is not excited about her princess duties. The voyage should be smooth sailing, but the tides are changing under the sea, a storm is brewing, and Izzy and Pipp are swimming right into it. Pirates and ghost ships are not the only dangers of the deep sea! Dive in with the Mane Six to get to the bottom of Seapony secrets.