The movie begins with the chipmunks and chipettes causing chaos on a luxury cruise. After Alvin performs a dangerous stunt with a kite, he, his brothers, and the Chipettes are washed overboard and marooned on a tropical island. They believe it's uninhabited—until they meet a castaway (Jenny Slate) who is hiding a secret.
Consequently, the availability of Chipwrecked on the Archive is inconsistent. One week the link works; the next, you are greeted with a "Item removed due to copyright claim" error. alvin and the chipmunks chipwrecked internet archive
Pro-tip: Look for collections labeled rather than the official "Movie Archive." Also, check the upload date—files uploaded within the last three months are more likely to be active. The movie begins with the chipmunks and chipettes