The Pirate Ship is a ship that serves as a means of transportation for Kuala and his pirates in Swiss Family Robinson. It is equipped with cannons used for firing at enemy ships and lifeboats for allowing them to sail to shore.
In the film
Kuala used this ship to chase the one that was carrying a family of passengers called the Robinsons, who were on their way to find a new life in the new colony of New Guinea, into a storm one night.
Two days later, in the morning, Kuala's ship was mistaken for a friendly one by Ernst Robinson that would help him and his family get off the island they were shipwrecked on. Luckily, Father was able to identify it quickly as the same one that chased them into the storm. Seeing as to how the Robinsons' ship, the Titus was stuck on the rocks and still having some passengers, Kuala ordered his pirates to fire on them with their cannons until Father managed to scare them off with a quarantine flag despite Fritz and Ernst trying to load a cannon to fight back.
A few weeks (or months) later, the pirate ship was seen with yet another one somewhere on the beach of the island the Robinsons had been staying on. It was mentioned that it was used to capture an British ship along with its captain and his granddaughter, Roberta, disguised as a cabin boy named "Bertie" to fool the pirates, to be used for ransom. At night, after Roberta was saved by Fritz and Ernst, one of the pirate ships was used to sail off the island while carrying Captain Moreland to take him back to England for ransom.
A few days later, the pirates used their ship to return to the island to look for the "boy" for more ransom. In the end, after a fierce battle between the pirates and the Robinsons, cannons were heard firing. As it turns out, they came from one of Captain Moreland's ships, having been ransomed, having returned to the island as well, and using them to fire on the pirates and destroying the pirate ship in the process.