Microsoft finds underwater datacenters are reliable, practical and use energy sustainably:

Microsoft put a server farm at the bottom of the sea and let it run for a few years.

The team hypothesizes that the atmosphere of nitrogen, which is less corrosive than oxygen, and the absence of people to bump and jostle components, are the primary reasons for the difference. If the analysis proves this correct, the team may be able to translate the findings to land datacenters.

Or will it means data centres are plonked all over the oceans?

“Our failure rate in the water is one-eighth of what we see on land,” Cutler said.

“I have an economic model that says if I lose so many servers per unit of time, I’m at least at parity with land,” he added. “We are considerably better than that.”

Worth following the link to read more detail and see some images of the subsea vessel.