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".

London and Bailey are on a mission to prove that Miss Tutweiller is dating Mr. Moseby after overhearing a conversation between the two. Meanwhile, Zack convinces Cody to sneak out after curfew to catch the Starlight Follies show on the ship. When they finally make it past the security guard and into the show, they become convinced that their teacher, Miss Tutweiller, is one of the showgirls by seeing her heart shaped anklet in the show, and during class, so Zack sends Bailey and London undercover as two showgirls to find out.

The ship is struck by lightning when it crosses the International Dateline, which places Cody in the same day over and over. He tries to use each day as a chance to let Bailey know how he feels about her, but something gets in the way every time. It's then up to Cody to divert the ship from the lightning to set them back on the right course.

The S.S. Tipton visits Greece. While they are there, Bailey crushes on the tour guide, which makes Cody jealous. To impress her, Arwin's cousin, Milos, gives him a replica of the ancient amulet of the Greek goddess Aphrodite to give as a gift to her, but in a mix up, he ends up getting the real one. Meanwhile, London has to write a speech for her father, who is funding a new exhibit, but finds it very difficult, but then has a dream about Greek history, which inspires her.

When Cody and Kirby don't allow Zack to bungee-jump off the side of the ship, the brothers accidentally knock Kirby off the ship, but Kirby lands in the hot tub. To make it up to him, Zack and Cody tutor Kirby so he can pass his high school equivalency exam to earn a better job. Meanwhile, London embarrasses Bailey on her internet show in a new segment called "Boo You!"

Zack and London play matchmaker for Mr. Moseby and Ms. Tutweiller, but with little success. Eventually, they get Moseby and Tutweiller together, and although they have an argument, they remain together. Meanwhile, Cody tries to impress Bailey by acting like someone else based on her dating test results. However, what Cody doesn't know is that some of her answers were for fun, while others were true.

As punishment for setting off a stink cloud, Zack is made hall monitor, a role which he takes way too seriously. After sending half of the school to detention, Zack experiences the repercussions of upsetting all of his friends. Meanwhile, Bailey gets a job at London's boutique, an extension of London's personal closet.

When Zack turns in one of Cody's old essays as his own, Ms. Tutweiller thinks he has a fear of bananas. Meanwhile, London goes through withdrawal when her cell phones are taken away in class.

Shortly after the start of a new semester on the ship, Zack, Cody, London, Bailey, and Woody are all cast-away on a life boat London was using as a closet and eventually find their way onto a deserted island. Cody's relationship with Bailey starts falling apart after an argument over wind patterns emerges and causes a fall out with the remainder of the group. Back on deck, Ms. Tutwieller and Mr. Moseby are put in exactly the same predicament as the others and even have the same disagreement over control of the operations. Cody and Bailey mend their relationship at the end of the episode.

Cody creates a web of lies to cover the fact that he didn't do his homework and it gets out of hand. Mr. Moseby and Zack get handcuffed together when their fighting gets worse.

While searching through an archaeological site in South America, Zack awakens the spirit of an ancient princess.

The gang all have dreams of being characters in three different fairy tales; Hansel and Gretel, Snow White, and Jack and the Beanstalk.

A class assignment requires the students to simulate marriage to learn the challenges that face married couples in everyday life. Cody 'marries' Bailey, Zack 'marries' London, and Woody 'marries' Addison. However, when the "Wheel of Life" gives Cody as injury, he and Bailey begin to fight.

While producing a news show for Ms. Tutweiller's class, each of the kids find their own set of problems. Zack and Bailey clash as co-anchors, Cody makes a shocking discovery linked to London during his investigative reporting, Kirby reminisces about the good ole days, while London is having trouble with the green screen.

Centuries in the future, Starship Tipton resident prankster Zerk (Zack's great-great-great-great-great grandson) plays a joke on feuding aliens and because of it, they vow to destroy the starship. The kids must travel to the future to save their descendants and fix the problem before it's too late. Meanwhile, London discovers that she has a great-great-great-great-great grandson, Rome, and that the Starship Tipton belongs to her family.

Cody leaves the ship following his break up with Bailey to join an elite, non-religious, monk-like club which he hopes will help him get over the break up. Zack and Woody are determined to go there and save Cody. Meanwhile, London and Miss Tutweiller try to console Bailey by giving her relationship advice.

The Seven Seas High dance is coming up. Having broke up, Cody and Bailey lie about having dates to the dance, so they quickly try to find a backup date to backup their lie. Now the pressure is on to see who has the best game. Meanwhile, Woody is tired of Tutweiller and Moseby arguing about who should get the skydeck for the school dance, so he makes them share the skydeck. It is revealed though flashback that Mr. Moseby and Miss Tutweiler's interest in the Middle Ages and 1980s, respectively, comes from the tribulations they endured as outcasts in their youth. Through understanding, Mr. Moseby convinces Emma that they both have become successful adults and have overcome their painful pasts.

Zack becomes attracted to a girl named Maya, but when he realizes he is actually falling in love with her, he attempts to use the six month plan Cody devised to date Bailey. Meanwhile, Dante, the boy who stole Marcus's identity in Paris, stows away on board to have Marcus produce his next album. In addition, Cody is trying to condition himself to forget about Bailey by flicking a rubber band against his wrist every time he thinks about her while she is visiting her home in Kettlecorn.

Zack, London, Woody, and Maya are all trapped in London's shoe submarine with only enough air for thirty minutes. Meanwhile, Marcus helps Cody prepare to play chess against a beautiful Russian junior champion.

London and Woody go to a posh beach club for senior ditch day, but when the bouncer won't let Woody in, London and Zack go without him. Meanwhile, in an effort to keep their perfect attendance records, Bailey and Cody show up for class, which annoys Ms. Tutweiller who was looking forward to her day off.

After assigning the class to write their own play, Ms. Tutweiler selects Cody's play to be presented in class. However, Bailey refuses to participate after realizing the play antagonizes her role in the break-up between her and Cody, forcing Cody to act as Bailey and Zack as Cody.

After the students pull a prank on Mr. Moseby, he cancels the senior prom. So, Zack comes up with a plan to have a "secret prom". Meanwhile, Bailey tries to get everybody to vote her for prom queen while Cody helps Woody ask Addison to prom. Ultimately, the kids award the roles of king and queen to Mr. Moseby and Ms. Tutweiller.

Mr. Moseby announces that London's dad, Mr. Tipton is selling the ship and that it will be dismantled within a week.