Data centers consume fresh water at rates that are creating real conflicts with municipal water systems and agricultural users. US data centers consumed 17 billion gallons in 2023, with projections reaching 33 billion by 2028. The logical question — why not use seawater instead — runs into a specific engineering problem that most operators have not worked around: salt.
Standard evaporative cooling systems spray water over membranes or cooling media to absorb heat through evaporation. Seawater leaves salt residue when it evaporates. That residue accumulates rapidly and clogs the system. The standard evaporative cooling architecture is fundamentally incompatible with seawater without expensive modifications. That single constraint has kept most coastal data centers drawing from fresh water supplies while sitting next to an ocean.
Wet Surface Air Cooling (WSAC): Seawater sprays over closed pipes carrying facility coolant. Salt builds up on the pipe exterior but can be flushed periodically with fresh water. Google uses this at its Hamina, Finland facility. Closed-loop direct cooling: Cold seawater from the ocean floor circulates inside sealed pipes — never contacting equipment. Used by Microsoft's Project Natick. Air-exchanger cooling: Cold seawater pipes chill facility air circulation, functioning like a CRAC unit with ocean water as the source fluid.
Google's Hamina data center in Finland repurposed a paper mill on the Gulf of Finland and built its cooling system around Wet Surface Air Cooling. The system sprays seawater over closed pipes carrying facility coolant — the seawater cools the pipes through evaporation, leaves salt deposits on the exterior, and those deposits are periodically flushed with a relatively small volume of fresh water.
The net result: the facility uses dramatically less fresh water than a comparable land-locked evaporative cooling system, while the seawater supply is essentially unlimited. The maintenance tradeoff — periodic pipe cleaning — is manageable at operating scale. The geographic requirement — coastal access — is a constraint but less limiting than it sounds. Many of the world's largest data center markets (Singapore, the Netherlands, coastal Virginia, Ireland) have direct coastal access.
Microsoft's Project Natick placed server pods directly underwater on the ocean floor off the Orkney Islands, using the cold ambient seawater as a passive heat sink. Cold water at depth runs at approximately 4°C year-round — well below any data center cooling requirement. The facility operated for two years with failure rates significantly lower than comparable land-based deployments, a result attributed partly to the nitrogen atmosphere inside the sealed pod and partly to the absence of human technicians introducing corrosion and contamination during maintenance.
The closed-loop seawater model — pumping cold deep water through sealed heat exchangers that serve direct-to-chip cooling systems — is technically straightforward. The challenges are civil engineering (marine pipeline installation, biofouling management) and regulatory (marine permitting, environmental impact assessment). These are not physics barriers. They are project development barriers that add cost and time but are solvable.
Northern European coastal markets — Denmark, Norway, Sweden, Finland, Iceland — have cold coastal water, low ambient air temperatures, and renewable energy from hydropower and wind. The cooling infrastructure case for these markets is already strong on air-side economization alone. Adding seawater closed-loop cooling to a facility already designed around Nvidia's 45°C warm-water specification creates a cooling system with near-zero water consumption, near-zero refrigeration energy, and heat rejection capacity that scales with compute load rather than against it.
The industry's water problem is real and growing. The solution for facilities that can access coastal resources exists and is operating at scale. The question is whether the project development friction of marine cooling infrastructure is lower than the political and regulatory friction of drawing fresh water from communities that increasingly don't want to give it.