Dave, The Chipmunks, and The Chipettes, go on a vacation on a cruise ship. The Chipmunks and the Chipettes, and especially Alvin, end up creating pandemonium. Later that night, after Dave leaves to eat at the captain’s table and apologize for Alvin’s behavior, Alvin sneaks out to the ship’s casino, followed by Simon, who hopes to keep Alvin out of further exposure; meanwhile the Chipettes go to the ship’s dance club, leaving Theodore alone in the room, watching an unsuitable monster movie. Dave discovers that his old boss, Ian Hawke, is working as the ship’s safety monitor dressed as a pelican, and is out to inform the captain if the Chipmunks and Chipettes cause more problems. Simon and Alvin are eventually caught in the casino, and are brought back to the room, along with the Chipettes, and all are accused by Dave for not being trustworthy. The next day, Alvin goes para-sailing on a kite, but the kite flies away with him and the other Chipmunks. Dave goes on a hang-glider to find them but Ian attempts to stop him, and they both end up in the Pacific Ocean.
Meanwhile, the Chipmunks find an island, and they sleep for the night. Dave enlists Ian’s help to find the same island and begin looking for the Chipmunks. The next morning, the Chipmunks go and find food and while doing so, an island castaway named Zoe shows up and sees the Chipmunks and Chipettes for the first time. They then go to Zoe’s tree house, where Eleanor sprains her ankle after falling off a zip line, and Simon gets bitten by a spider, the side effects including personality changes and loss of inhibition.