About the Water 7 Arc
The Straw Hats arrive at the oceanic metropolis of Water 7 to find a shipwright who can repair the Going Merry, as well as potentially join their crew. They soon become targeted by the Franky Family, the city's underground gang, and become involved in a plot within the Galley-La Company. Between the disappearance of Robin and a schism that develops between Luffy and Usopp, the crew begins to fall apart.
After being attacked by Aokiji, the crew was fully recovered and had returned to sailing. Along their way, the crew saw a giant frog doing the crawl stroke and, wanting to eat it, Luffy ordered everyone to make the ship follow after it. They ended up on some tracks underwater and were nearly run over by a train traveling on top of the water, and the frog was sent flying by it. They were amazed by this sight.
On a nearby station, they met with the stationmaster named Kokoro and her granddaughter Chimney, along with her pet rabbit (who acts like a cat) Gonbe. After revealing that the frog, Yokozuna, was perfectly fine and that it was always testing its strength against the train, Kokoro explained that the train was a Sea Train that connects several of the nearby islands and is called the Puffing Tom. She then told them that the Log Pose would lead them to Water 7, a city of shipwrights where they could fix their ship, and told them to get help from a man named Iceburg.
The crew arrived at the city, which resembled a fountain, and sailed through the canals in the city looking for a place to dock, but the people were kind enough to tell them where to hide their boat. After stopping, a group of Luffy, Nami, and Usopp headed out to exchange their gold from Skypiea and find a shipwright, using creatures called yagaras to navigate the canals.