Shellfish Island

From a distance, the place reads as an ordinary tropical isle: pale beaches, dense greenery, and a single broad rise that arches across nearly its entire surface. That surface is a disguise. Beneath the soil and roots lies the heavy shell of an enormous oyster, which spent so long lying still that sand and plants took hold over it. Once the shell parts, its halves show a faint purple tone scored with deep grooves, and the cavity within cradles a pearl towering at roughly three times the height of a grown person.

The island earns its alternate nickname, Treasure Island, by being exactly what its surface denies. Positioned somewhere between Mamana Island and Samua Island, though neither is ever depicted, it served as a hideout and a hunting ground at once. Amanda's father camped on it while chasing the prize, and his children, joined by Maccus and Bonney, sheltered there while dodging the Bayan Pirates and continuing the search he had begun.

The oyster's transformation into a false island took ages of stillness and accumulation. Amanda's father, hearing rumors of a fabulous fortune, partnered with Bayan to locate it, only to be betrayed and badly hurt. Wounded, he handed his children an Eternal Pose pointing to a neighboring island, a tool for reading maps, and a chart inked on his eldest daughter's back, trusting them to finish what he could not. The children were seized by the Bayan Pirates, broke free with help from Maccus and Bonney, and made their way to the island to dig for its secret.

The Straw Hat Pirates later arrived and quickly saw through the escapees' family act and their treasure hunt. After Zap abducted Amanda and Luffy, prompting a rescue run, the group returned and assembled the father's clues. Luffy, Zoro, and Sanji dropped into one of the caves and severed three fleshy stalks, which turned out to be the muscles clamping the shell shut. The halves swung open to expose the oyster's true form and the colossal pearl inside, letting Amanda finally grasp her father's dream and the cost he paid for it.