Look at this beautiful pearl. It mesmorizes Fishmen, explained Casas, showing you a gleaming pearl.
First eliminate the Fishmen surrounding the merchant ship. When they're out of the way, I can recruit helpers to search through the wreckage.
Place this pearl near the wreckage to lure out the leader of the Fishmen, then defeat him!
Once you defeat their leader, the rest of the Fishmen will return to the bottom of the sea in fright. They're cowardly at heart.
After you eliminate the leader, don't waste any more precious pearls. They're invaluable.