Undersea Volcanic Eruption! Swept into Fish-Man Island

The Flying Dutchman surfaces and Vander Decken orders Wadatsumi to crush the Thousand Sunny, but the Kraken intervenes and overpowers him. When the volcano erupts, the crew scrambles to escape. As Surume leaps off a cliff and falling boulders threaten the ship, Usopp briefly holds them back with his new technique, Sargasso. The celebration is cut short when a rock strikes Surume's head, knocking it out as they plunge into the depths. At the bottom they finally find Fish-Man Island, only to be stopped at the threshold by a band of sea monsters and a figure riding them.

The Kraken defeats Wadatsumi after Vander Decken commands the attack. The undersea volcano erupts, forcing a desperate escape. Usopp debuts his Pop Green move Sargasso to shield the crew from collapsing rock, but a stray boulder fells Surume, sending the group sinking toward the seafloor. Fish-Man Island comes into view, and the crew's approach is blocked at the entrance by hostile sea beasts and a mysterious rider.

The episode introduces Hammond as well as the Sea Forest location and Fish-Man Island itself, alongside Usopp's Sargasso technique. The preview for the next episode is trimmed shorter than its usual length.