London, Zack, Cody and Mr. Moseby set sail on the S.S. Tipton for their semester at sea. London convinces her roomate to leave the ship so she can have a room to herself. Cody finds himself sharing a room with Woody, who is very messy, and Zack shares a room with Bailey, who is a neat freak. Nobody knows that Bailey is a girl who disguised herself as a boy in order to gain a position on the ship after she found that there were no more vacancies for girls. Zack and Cody agree to switch roommates, but Zack changes his mind after he finds out that Bailey is a girl. After everyone else eventually finds this out Bailey is allowed to stay, filling the position vacated by London's ex-roommate, and Bailey becomes London's new roommate. This is the last straw for London and she escapes to Parrot Island via helicopter.

When the S.S. Tipton makes a special trip to pick up London from Parrot Island, Bailey, Moseby and Woody find themselves in jail because all the parrots left for Seal Island after Tipton Industries cut down all the trees. It's up to Zack and Cody to get them out of it but Zack and Cody end up in jail along with the others, and Bailey has to use her pig, Porkers, to rescue them. Zack and Cody fight for Bailey and Zack lets Cody have her after finding out about her ex-boyfriend Moose and seeing she has too much "baggage".

When Bailey starts feeling homesick, Cody decides to recreate her hometown festival. However, thanks to London, Bailey's hometown boyfriend, Moose, shows up. He and Cody compete in corn bobbin', arm wrestling, and chess to win Bailey's heart, but Cody loses every competition. Moose asks Bailey to come home, so she asks Cody what to do. Cody says to follow her heart and Bailey stays because she would miss her friends

Zack is surprised to learn that he has a new roommate who used to be a famous rapper until he hit puberty and his voice got deep.