East and West Lakes

The East and West Lakes are two large bodies of water located in the central Earth Kingdom to the southwest of Ba Sing Se. They are divided by the pinnacles of rock that form the Serpent's Pass, and connected only by a small gap in the rock in the middle of the pass. Both lakes are connected by rivers to the sea, with the West Lake connecting to the Mo Ce Sea and arctic seas, and the East Lake to the large gulf southeast of Ba Sing Se.

History
At some point prior to Avatar Aang's return, the Fire Nation gained control of the West Lake from the Earth Kingdom, and sent patrol boats along the Serpent's Pass to scan for intruders. Rumors spread that the Fire Nation was working on a secretive project in the West Lake and didn't want anyone investigating. The East Lake, however, remained under Earth Kingdom control, with one of its harbors, Full Moon Bay, serving as the main transfer point for refugees headed to Ba Sing Se. Chameleon Bay, another cove at the mouth of a river which led to the outskirts of Ba Sing Se, was being guarded by the warriors of the Southern Water Tribe under the command of Chief Hakoda.

However, after the Earth King was overthrown, the Fire Nation, under the command of Admiral Liang, quickly swarmed into the East Lake, forcing the Water Tribe forces along with Aang, his friends and the Earth King to abandon this defense, in any case it was no longer needed. After scuttling the Water Tribe fleet in the center of the East Lake and commandeering a Fire Nation patrol vessel, they fled west, only to encounter a barrier constructed by the Fire Nation to control traffic through the gap in the Serpent's Pass. Hakoda and Sokka managed to convince the barrier guards to let the ship into the Western Lake, only to run into a patrol ship from the Eastern Fleet. After mistakenly revealing themselves to the ship's commander by commenting on having received orders from Admiral Chan, who was in reality on leave, they engaged in a skirmish with the ship. However, they managed to escape with relatively little damage.