Star Wars: Shards
Pelagon is the capital of Pelagia Province, and the effective center of all travel through the system. Its eponymous planet is primarily oceanic, with a very pleasant climate and two large platforms that each support a “seascape” city above the waterline.
Vorkosigan Surleau is located here, in a restricted section of capital city Pelagar.
At the bottom of the ocean are some ancient ruins that are at least 13,000 years old.
The oceans are in pretty bad shape, undergoing detoxification, because eighteen seascapes got bombed to smithereens by House Mecetti and the Galactics during the purge.