A map set in a fantastical sci-fi ocean, completely underwater. Shallower areas could have Seagrass Plains, Coral Forests (perhaps large spindly coral somewhat shaped like trees, with glowing parts?), and Kelp Jungles (maybe similar to Subnautica's kelp forest?). Some kind of dome or bubble could be in the shallows, where the player spawns in. Smaller bubbles or structures could offer resources unavailable in the ocean, like animals and plants. In the deep areas there could be Fossiliferous Volcanos, a biome with smaller volcanos and geysers with a bunch of fossils and rare ores, and the Deep Void, a nearly empty chasm of dark waters with the occasional spooky anglerfish (a small structure, I imagine).
i'm not seriously suggesting this as a whole map, i know it would be a ton of work, but i hope some of my ideas give you inspiration :3
