User blog comment:Owlfeathers0117/An idea to make surface ships useful again./@comment-11135771-20141217044207/@comment-11135771-20141217060900

The water only boils near the geothermal vents. The rest of it is warm, but not that hot (it still creates water vapour that comes through the vents though, since the air above the stone crust is quite cold). On average I'd say it's like 30°C, warmer near the geothermal sources, and colder near large steam vents.

As for who discovers it, not sure. I'm thinking maybe the SAA, as they do a fair bit of exploration, have a base on Neo-Earth, and would be likely to share the discovery.