The Geyser Sea was a body of water located on the planet of Akuria II. The sea was kept warm through a system of hot geysers beneath it that also seemed to have the effect of changing the color of the water to an orange hue. The Akuria Rebel Base was internally heated by diverting a portion of the Geyser Sea into the base.
After Leia Organa and Luke Skywalker discovered his true identity, the Imperial commander who had been impersonating the Rebel leader Odan trapped Luke inside a runaway War Sled that was careening toward the Geyser Sea. Luke was rescued by Odan, Fafnir, C-3PO, and R2-D2 at the last moment.