When Captain Dreadbeard and his Pirates invaded the islands, all of the Mabu were taken prisoner when they lost to the pirates' card games. The Shipmaster tried to stop the pirates, but he was eventually captured himself. When the Skylander arrived at the Coconut Islands with the motive of liberating the town, the Shipmaster was the first Mabu citizen that was freed (after a card game with Fangs, who was keeping him as a prisoner).
After the pirates made their escape with the town's treasure, and with Jess LeGrand, the Shipmaster allowed the Skylander to man their own pirate ship to chase the pirates down to Plunder Island. While the Skylander steered the ship, they also gave commands to the Shipmaster to fire the cannons at Plunder Island's defenses.