BriGuy
Life of the Party
Heat on Earth is dissipated through air and water (convection and conduction). In a vacuum, there are no particles to carry heat away from server racks. A vacuum flask (Thermos) keeps coffee hot precisely because a vacuum is an exceptional thermal insulator. The idea that the vacuum of space offers "free, effortless cooling" is one of the most common misconceptions in physics.
Microsoft has been looking at building them underwater for quite a while. I'm not sure if any have been built. I know the Chinese have been considering them, too.
Microsoft finds underwater datacenters are reliable, practical and use energy sustainably - Source
Microsoft retrieved the Northern Isles underwater datacenter from the seafloor off Scotland's Orkney Islands. Project Natick is proving the concept of underwater datacenters is feasible as well as logistically, environmentally and economically practical.
news.microsoft.com