20,000 Leagues Under the Sea is a track ride in Mysterious Island at Tokyo DisneySea. While it's not a "must do," it is also recommended.
On board, you're sitting on one of three two-person benches inside the submersible, each with its own window. Using your joystick, you can control the lights that illuminate some of the mysteries awaiting your discovery in the deep. You're searching for the lost continent of Atlantis, and along the way, you will encounter a ship's graveyard in "Kraken Reef" and a surprise encounter in "Lucifer's Trench."