When Gill Grunt, Zap, and Wham-Shell arrived in the Kingdom of the Merpeople to find information on the Water segment to the Mask of Power, they discovered that the kingdom was deserted, with only a few remaining, including King Scalebeard, Princess Finella and Prince Aquan himself. Although the merfolk themselves have no clue what happened to the other mer citizens, Prince Aquan, Princess Finella and a few other merfolk soon fell under a strange trance and swam out of the kingdom without a word, with the Skylanders following after them to see where they were going.
During the chase, Wham-Shell mysteriously had fallen under a spell and turned on Gill Grunt and Zap, capturing the latter and dragging the nearly unconscious water dragon into a cave where the hypnotized merfolk went into. Gill Grunt soon managed to get inside and discovered that Wham-Shell and the merfolk were being controlled by Captain Grimslobber, who was using the Fish Master's Crown to enslave the merpeople and force them to haul out gem-eels and ship them to the surface where Grimslobber would become rich.
Gill Grunt, after being hypnotized himself, managed to break free of the Fish Master's curse and saved the merpeople, Prince Aquan and Princess Finella from the trance. As Grimslobber made a hasty retreat, Gill Grunt hung onto the diving bell the pirate captain was in and cronfronted the seadog and his crew on board the Fearsome Fang. With the help of the freed merfolk, Zap, Wham-Shell, and even Spyro the Dragon, the Gillman bested Grimslobber and his pirate crew. Prince Aquan and Princess Finella presumably returned to their kingdom afterwards.