First, let me say this is a world that I'm making it myself. I want feedback on my ideas, if you are willing to give it.
I'm planning to have the entrance in Nexus Tower. There will be a terminal similar to the one for Crux Prime. The world will also be on Crux Prime, only underwater.
The console will take you to an underwater base. The base will be in the style of the divers in the Atlantis line. I plan on the base to be 2 stories tall, with both stories combined be about the height of the hallways in the Nexus Tower. There will be about 4 NPCs, 1 gear vendor, and 1 model vendor. There will also be one big lobby area with a portal/gate thing that keeps the water out. You can only pass through the gate if you have on one of the 3 pieces of dive gear. I will post a picture of it after I make it.