Freddi Fish visits the house of Grandma Grouper, where she learns that someone stole Grandma's treasure chest of kelp seeds, which provides the food for the whole ocean. Freddi cheers Grandma Grouper up by promising to find the treasure for her. After leaving Grandma's house, Freddi and her friend, Luther, discover a bottle with a note lodged inside that gives a clue to the treasure's location and they set out to look for more clues. Unbeknownst to the two, it was two sharks named Boss and Spongehead who stole the treasure as part of their plan to help their boss, the Squidfather, grow kelp; Spongehead had hidden four bottles in random locations to lead his way back to the treasure. Eventually, Freddi and Luther find the fourth and final bottle, revealing that the treasure is hidden in a sunken ship.