!! Short Summary
A filler arc set after the ''[[Recap/OnePieceDavyBackFightArc Davy Back Fight Arc]]''. One night as the crew rest, a boy with a seahorse-shaped flute plays it near the ship. The next day the crew awaken with their memories of each other wiped out, except for Robin. It's up to her, who was the only one not affected, to get the crew's memories back and find out the cause of it.

!! Main Summary

''Ocean's Dream Arc'' has the following tropes:

* AmnesiaEpisode: The main plot has a seahorse stole all the memories of the protagonists (with the exception of Nico Robin) since they are joined in the Straw Hat crew. At the end, Luffy defeat the seahorse and all return to normality.
* TheAnimeOfTheGame: Based on a UsefulNotes/PlayStation and UsefulNotes/GameBoyAdvance game that was released at the time.
* {{Callback}}: The seahorse is doing all this so he can become a Millennium Dragon which viewers may remember from the ''[[Recap/OnePieceWarshipIslandArc Warship Island Arc]]''.
* CharacterizationMarchesOn: The Straw Hats go back to their original characterizations when their memories are taken, with Sanji's flirtiness being less {{Flanderized}}, Chopper being much more shy, Nami being distrustful of the Straw Hats, etc.
* ChasedByAngryNatives: The Straw Hats at the end of the arc.
* TheDogWasTheMastermind: The seahorse "flute" is sentient and the cause of the whole dilemma.
* HeroWithBadPublicity: The crew is blamed for the memory loss of the island after defeating the seahorse.
* LetsYouAndHimFight: The second time Luffy and Zoro fight.