During a cruise, for a family vacation, the Chipmunks and Chipettes turn the ship into their personal playground causing trouble and running amuck as they will. Dave (Jason Lee) notices that the Chipmunks/Chipettes old manager Ian Hawke (David Cross) working as a safety monitor on the cruise. Alvin goes parasailing on a kite and he flies away with the other chipmunks. Dave goes on a hang glider to find them with Ian and they both end up in the ocean.
Meanwhile, the six chipmunks find an island and they sleep for the night. Dave enlists Ian's help find the same island and begin looking for the six chipmunks. The next morning, the chipmunks go and find food and while doing so, an island castaway named Zoe (Jenny Slate) shows up and sees the...