The Underwater Base is a location seen in Lilo & Stitch: The Series.
It only appears in the crossover episode "Rufus", and is used as Dr. Drakken and Shego's lair. Hämsterviel hires Dr. Drakken to kidnap Stitch and secure him in an underwater base, where both Drakken and Shego can prepare to clone him. When Kim goes out to find the base and rescue Stitch, she gets sucked in a current ("People Eater") and is also taken hostage. Eventually, Stitch and Kim are rescued from their prison by Lilo and Rufus. Everyone then manages to escape the underwater base.