By Charlotte Reid 
An underwater data centre developed by Chinese maritime technology company Highlander is under construction at a shipyard in Nantong, in the eastern Chinese province of Jingsu, on 11 September 2025.
In two weeks’ time, the Chinese company Highlander is set to submerge its first data centre in the Yellow Sea, off the coast of Shanghai. These powerful infrastructures, which are essential to the smooth running of our digitalised societies, generate unwanted heat, requiring a lot of water and energy for cooling.
Hence the hope of reducing this energy bill by submerging the data centre directly into the depths. Underwater, the servers benefit from natural cooling by sea currents. With this first centre, Highlander wants to validate the commercial viability of this immersion technique. Microsoft conducted an experiment off the coast of Scotland in 2018, but abandoned the idea in 2024. ‘Underwater facilities save around 90% of the energy used for cooling,’ says Yang Ye, Highlander’s vice-president, who is leading the project with public companies. The company will serve customers such as China Telecom and a public company specialising in artificial intelligence.
Environmental impact
To complete the construction of this project, the company had to ‘face greater challenges than expected,’ says one engineer. To ensure the structure is watertight and protected from corrosion, the company is using a special coating made of glass particles, which is applied to the steel capsule containing the servers. Assembled on land in several components before being submerged, the data centre will be powered 95% by nearby offshore wind farms.
Many voices are questioning the environmental impact of such a structure. The heat generated could attract certain species, repel others and disrupt fragile ecosystems. Highlander claims that an independent assessment conducted in 2020 during a test near Zhuhai, in southern China, showed that the surrounding water temperature remained well below acceptable thresholds.