Microsoft has sunk a tank full of internet servers into the sea off Orkney.

It is part of a project investigating whether storing a data centre under water can make it more energy efficient.

Microsoft engineers believe the cold water of the North Sea may help cool the data centre - a major cost for similar facilities on land - but it will be impossible to fix the servers if they break down.

The data centre, which acts as a repository of online information, was dropped into the sea this week at the European Marine Energy Centre.

"We know if we can put something in here and it survives, we are good for just about any place we want to go," said Microsoft's Ben Cutler.

Storing data centres under water near coastal cities could improve web browsing, video streaming and online gaming, according to Microsoft, as well as boosting cloud-based artificial intelligence.

Peter Lee, corporate vice-president of AI at Microsoft, added: "If we can be within one internet hop of everyone, then it not only benefits our products but also the products our customers serve."

Project Natick's 40ft Orkney data centre is loaded with 12 racks containing 864 servers.

It was assembled and tested in France and shipped to Scotland on a flatbed truck, where it was attached to a ballast-filled base and dropped to the seabed.

The Project Natick team will spend the next 12 months monitoring the performance of the data centre, checking everything from power consumption and humidity to sound and temperature.

Mr Lee added: "We are learning about disk failures, about rack design, about the mechanical engineering of cooling systems and those things will feedback into our normal data centres."