After Billy, Mandy and Grim are disappointed with the SassyCat amusement park submarine attraction, Grim uses his powers to take them to the bottom of the ocean to have a real magical adventure. There, they are sentenced to death for trespassing into the Googen Kingdom by King Triceps, a wrestling merman. However, the king's daughter, Hariel, also a mermaid, stops the sacrifice and tries to marry Billy in order to inherit the kingdom. Then, it is revealed that King Triceps is actually Hariel's sister, the sea witch Uvula, who also tries inherit the kingdom. A cat fight ensues between the two ladies, which ends when Billy agrees to marry both of them. Then, the plot is eventually revealed to be a story Billy is telling to Miss Butterbean, who initially asked him what happened to his report.