The Dashing Sea Train and the City of Water: Water Seven!

Fully mended after Aokiji froze them, the Straw Hat Pirates once again have the Going Merry underway. As they sail, Zoro notices a huge frog swimming a crawl stroke and points it out, so Luffy has the ship give chase. Peering through her telescope, Nami puzzles over a lighthouse standing on a nearby island and figures people must live somewhere close.

The pursuit ends abruptly when the Merry strikes something unseen and a rumble builds around the hull. A signal light appears, and then a steam engine barrels straight at the crew across the sea. Nami shouts for an immediate about-face as Luffy reels from the impact. The train rushes by with almost no clearance, leaving Sanji, Usopp, and the others astonished that any machine could ride the ocean in such a shape. Deaf to Luffy's warning, the giant frog meets the engine head-on and is knocked out cold.

A small girl spots the pirates near her home and calls for her grandmother, who fumbles with a Den Den Mushi and then forgets whom she meant to reach. Once the two sides relax and warm to one another, introductions follow. The grandmother is Kokoro, the girl is Chimney, and Chimney keeps company with a pet rabbit named Gonbe. Kokoro wonders aloud whether the strangers are train thieves before Luffy offers his own greeting.

Chimney explains how the sea-crossing locomotive functions. Rails lie hidden beneath the waterline, and the steam-driven engine called Puffing Tom holds to a set daily route along them, carrying passengers, cargo, and supplies from island to island. She also names the flattened frog as Yokozuna, a stubborn creature that repeatedly tests its strength against the train and simply will not die, causing the station endless trouble. Kokoro then rattles off the enjoyable stops the line serves, naming San Faldo, Pucci, and St. Poplar.

This episode kicks off the Water 7 Arc. Chimney, Gonbe, Kokoro, and Mishoin Cashible all debut here, and Water 7 itself is seen for the first time. DVD editions present the episode in its original 16:9 frame, while the analog broadcasts remained cropped to 4:3. Aokiji appears briefly in flashback. Following their conversation, a map to Water 7 passes from Kokoro to Luffy, and Luffy, Nami, and Usopp go on to purchase boats towed by the sea creatures known as Yagara.