Underwater AI data pods off Hainan

China has moved a commercial data center onto the seafloor off Hainan, using seawater as a giant cooling system instead of relying on land-based chillers. (news.cn) The site is off Lingshui in south Hainan, where a new 18-meter-long, 3.6-meter-wide data pod was lowered about 30 meters underwater on Feb. 18, 2025 and linked to an earlier subsea module first deployed in March 2023. Each pod can house more than 400 high-performance servers. (news.cn) Power usage effectiveness, or PUE, is the ratio between a data center’s total power draw and the power used by its computing gear; 1.0 is the theoretical floor. The Hainan builder has said the cluster runs around 1.1 PUE, while an earlier Highlander test unit posted 1.076. (chinadaily.com.cn) (highlander.com.cn) That matters because cooling has become one of the biggest costs in the artificial-intelligence buildout, especially in hot coastal cities where land, water and power are tight. China Daily said the Hainan pod can deliver up to 1,400 peta floating-point operations per second on a 1-megawatt reference power allocation, which the project manager said was about 40 percent more efficient than land-based centers. (global.chinadaily.com.cn) The Hainan cluster is aimed at artificial-intelligence training and inference, industrial simulation, game development and marine research. Xinhua and China Daily reported that nearly 10 companies had signed agreements by March and April 2025. (news.cn) (global.chinadaily.com.cn) Named customers have been reported, but not the full roster in current official accounts. China Daily reported in November 2023 that users included China Telecom, Tencent and Sanya Yazhou Bay Science and Technology City; Light Reading also said early customers included China Telecom, Tencent and SenseTime. I did not find a primary source confirming Alibaba as a client. (usa.chinadaily.com.cn) (lightreading.com) The project has been framed as part of China’s push to keep more high-demand computing near the coast instead of sending all workloads inland. Highlander said in 2022 that subsea centers were meant to cut the energy cost of “hot data,” meaning latency-sensitive services that need to stay close to users, and said its Hainan demonstration project was built to fit China’s broader East Data, West Computing strategy. (highlander.com.cn) The engineering pitch is simple: seal the servers in a pressure vessel, sink the vessel into cold, low-oxygen water, and move data back to shore through a coastal station. Project executives have said that environment reduces cooling demand, corrosion and hardware failures; Xinhua cited a semiannual report by China Telecom Hainan and the China Academy of Information and Communications Technology saying the site had recorded zero server failures since its 2023 launch. (english.scio.gov.cn) (global.chinadaily.com.cn) Hainan is not the first underwater data-center experiment, but it appears to be the first one operating as a commercial service at this scale. Microsoft’s Project Natick tested 855 servers off Scotland and later ended; Data Center Dynamics reported in 2025 that Microsoft had confirmed the effort was no longer active. (datacenterdynamics.com) (www.scmp.com) For now, the Hainan story is less about a futuristic stunt than about where the electricity bill goes. If the pods keep landing customers and holding their efficiency numbers in tropical water, the seafloor starts to look less like a lab and more like industrial real estate. (news.cn) (global.chinadaily.com.cn)