In the 1870s, Jules Verne wrote a pair of books about a man who called himself "Nemo" ("no one") who created an underwater vessel that was often mistaken for a sea monster. Both of these books are in the public domain, and can therefore be adapted by anyone. The second book in particular would make for an interesting series of Tall Tales, since the submarine itself is trapped under a volcanic island, but some of its gadgetry could be used.
The first tall tale would start at a new NPC, "Aronnax" who sets up a small dock on one of the uncharted rocks in the Devils Roar. He claims to have escaped from a madman in an "iron Fish" when a Kraken attacked, and offers a Tall Tale book. The first Tall Tale in the series "In search of the Nautilus" has Aronnax fit a diving bell on the back of the player's ship. The Diving bell takes the place of the rowboat docking station, and prevents the ship from being able to use a rowboat. The diving bell contains a storage locker (Standard Storage crate) and an ammo box. It is entered from below by a short ladder and has a floor that covers half of the inside, as well as portholes allowing a 360 degree view. By activating the controls of the diving bell from inside, the right and left buttons on the mouse (equivalent on a controller) moves the bell up and down at about 10 feet per second. It is always full of breathable air, so it acts as a platform that can be used to explore caves deep underwater where you would normally start drowning by the time you reached them, let alone get deep inside.
The tall tale is a search for the elusive "Iron fish" and Captain Nemo himself, which is in one of several new underwater caves beneath the various volcanic islands in the devil's roar. Completing the Tall Tale and reaching Captain Nemo unlocks the diving bell as a ship customization option, and the ability to do Nemo's tall tale, which also involves using a diving bell to search various deep sea caves and shipwrecks for clues as to the whereabouts of a sunken city where merfolk actually live. Upon completion of Nemo's Tall Tale, it unlocks a hat which is actually a diving helmet for purchase (20,000 Gold) And a steampunk-looking Eye of Reach (20,000 Gold) from Nemo. The helmet doesn't actually let you breathe underwater, and like all items in the game is purely cosmetic.
