The Suite Life on Deck - Season 1 - Eps 18: Splash & Trash
Zack and Woody are convinced that a girl the S.S. Tipton rescued from the ocean is actually a mermaid. They make multiple attempts to prove it, but are unsuccessful. Upon her telling Zack that she is really a competitive swimmer and extremely busy training for the Olympics, Zack decides to teach her how to relax. Meanwhile, Cody is fired as the ship's towel boy after he doesn't allow passengers to use multiple towels in an attempt to protect the environment. He also puts up a show to portray the future of the Earth if this kind of overuse continues, which ultimately gets him re-hired as towel boy.
About The Suite Life on Deck

Title: The Suite Life on Deck
First Air Date: 2008-09-26
Last Air Date: 2011-05-06
Status: Ended
Rating: 7.806/10 (from 500 votes)
Language: EN
Seasons: 3
Total Episodes: 73
Network: Disney Channel
Genres: Comedy, Family, Kids
Production Companies: Bon Mot Productions, Danny Kallis Productions, It's a Laugh Productions, Walt Disney Television
Synopsis
Zack and Cody Martin are aboard the SS Tipton, a luxury passenger cruise liner owned by London's father. The ship cruises the world with tourists and students who attend classes at Seven Seas High, the one high school that London's dad thinks will make his daughter a better student. While out at sea, Zack and Cody still have their compass pointed towards mischief, and London learns to live a "fabu-less" lifestyle, including sharing a small room with Bailey, a country girl from Kansas.
Cast

Dylan Sprouse
Zack Martin

Cole Sprouse
Cody Martin

Debby Ryan
Bailey Pickett

Brenda Song
London Tipton

Phill Lewis
Marion Moseby