The Great Treasure Contest! Collapse! Spa Island

The whole Spa Island resort turns out to be a front, with its owner Doran quietly working alongside Foxy to obtain a secret ingredient for a prized gem. When Lina admits she has hunted across every deck without spotting her missing sister Sayo, Luffy settles on a drastic answer: smash the entire vessel apart. Zoro backs the idea, Franky is left guarding the Sunny, and the rest of the crew begin wrecking the ship while battling through Doran's hired thugs, flooding compartment after compartment in the process.

Cornered, Doran wheels out an enormous cannon and parades Sayo, bound on the roof and locked in its firing line, demanding the research notebook in exchange for her life. A flashback shows the sisters' father and his work on the gem, fueling Lina's resolve to refuse the trade. Robin pins Doran with Seis Fleur, Usopp scorches his mouth with a Special Tabasco Star, and Zoro carves the cannon open with a Great Buddha Slayer to release Sayo. Luffy shifts into Third Gear and crushes the weapon with a Gigant Axe, splitting Spa Island in half and finishing the greedy owner off.

This installment carries no opening narration. After the rescue the crew discovers that the X on the father's map marked an X-shaped undersea volcano gaping below the island, and a circular rainbow, the so-called gem of the sea, blooms overhead. Days later Nukky, in bird form, delivers word that Lina and Sayo finished the gem; Luffy then fumbles it during a fall of candy rain, prompting Nami's furious order to recover it. The episode debuts Zoro's anime-only Dai Tetsugiri technique.