I learned so much in this project. I couldn't find information on how to use volumetric fog specifically in an indoor space—ie, without an HDRI cubemap or skylight to drive the colours—so I figured out that I could use a scene capture object, create a render target and make a static texture from it, then use that as the cubemap. Voilà, cool accurate-ish fog.
I also followed a tutorial to make procedural spline mesh blueprints which totally sped up my process of making nice cables that are easy to manipulate in-engine, and took the standard out-of-the-box water shader and expanded it to add emissive depth to get that nice glowy underlit goo effect. I'm really pleased at how these elements turned out. I'm not sure of how optimization friendly the goo is but for a beauty pass it's super neat.