User blog comment:Owlfeathers0117/An idea to make surface ships useful again./@comment-11135771-20141217044207/@comment-11135771-20141217053351

That's part of what makes it a difficult environment, requiring new tactics and innovation.

Except for near the steam vents, almost everywhere is pitch black. Some of the native plants and animals might be bioluminescent (although neither bright enough nor common enough to depend on as a light source), and there would be some underwater geothermal vents, but aside from that it's going to be very difficult to see anything.

Entire fleets with radar/sonar stealth could potentially sail right past each other without even knowing. Then there's the option of using lights, but there is also risk involved with that. Lights will make your position known to any enemies nearby, as well as potentially drawing the attention of the hungry and sun-deprived creatures below the surface. On the other hand, you could also use them to trick your opponents.