One Piece 607

The Straw Hats escape from the erupting undersea volcano...

...but their troubles are far from over.

Summary:
The undersea volcano erupts and forces both the Straw Hats and the Flying Dutchman to run for their lives. The current caused by the eruption push the kraken and Straw Hats downwards and sends the Flying Dutchman and their two sea monsters upwards. Nami realizes that Fishman Island should be inside the trench just ahead, and on Luffy's command the kraken jumps into the trench with the Sunny in tow. Debris from the eruption starts raining down on the Straw Hats and the kraken. Usopp manages to stop some of the debris with a giant sea grass pellet, but the kraken gets hit in the head by a boulder and falls into the abyss along with the Straw Hats.

Some time later, the Straw Hats wake up and find themselves at the bottom of the trench with the giant, brightly bubbles of Fishman Island within sight. The Straw Hats are about to head to the island, but they find their way blocked by several giant sea monsters and even the kraken is afraid them. The sea monsters are being ridden by fishmen who claim to be the New Fishmen Pirates. The pirates correctly identifies the Straw Hats and asks Luffy to join them or be destroyed. While the fishmen are talking to Luffy, Nami tells Franky to get ready for a big burst of air to shoot the ship into Fishman Island. Nami knows that Luffy will not agree to the fishmen's demands, but the crew is at a severe disadvantage at 10000m under the sea. As Nami and company are making preparations for the escape, Luffy answers the fishmen pirates with a big fat no.

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So we are finally at the fabled Fishman Island. On the way here, the Straw Hats managed to tame a kraken and escape from both a "ghost ship" and the undersea volcano, but their undersea adventure and troubles have probably just begun. The Straw Hats might be powerful, but they haven't fought fishmen under the sea yet, so chances are they'll need some sort of training or special equipment to be able to beat fishmen in water. As such, the Straw Hats will probably make it into Fishman Island with Nami's plan, but the Fishman Pirates and other people will continue to dog them. The Flying Dutchman and their two sea monsters will probably reappear sooner or later as well. It'll probably be a few more chapters before we know where this story arc is headed.