As Europe turns to renewable sources to diversify energy supplies away from Russian oil and gas, a peaceful marine scene conceals a billion-dollar security headache.
Rising above the Baltic Sea less than 10 km (6 miles) off the coast of Denmark, 161 wind turbines spin slowly. They supply around 4% of the country's power, sent to shore through two cable connections.
The turbines have no barriers or surveillance.
"Our technicians are only here until five o'clock in the afternoon, then they go home," said Thomas Almegaard, head of operations at Nysted wind farm, co-owned and operated by Denmark-based Orsted, the world's biggest offshore wind developer.
"If the Russians wanted to cause damage, they could do it easily," he told Reuters aboard a service vessel as it sailed through the wind farm.
"We don't do any monitoring."
The picture is similar across the North and Baltic Seas, Reuters found in a survey of 13 governments and interviews with a dozen lawmakers, regulators, military and industry officials. European states and companies are only now starting to monitor and secure their windfarms, the reporting showed.
Developers like Orsted think governments should take the lead and help provide the billions of dollars needed to protect their infrastructure. But even as North Sea countries alone plan to install enough wind power for more than 100 million homes by 2030, governments are still considering how much they can spend to safeguard such offshore assets.
Time is short: The EU has a legally binding goal to nearly double renewable sources as a share of total energy by 2030, to 42.5%, requiring a rapid expansion of offshore wind.
The risk was underlined last year with attacks by unidentified saboteurs on the Nord Stream pipeline. Again this month, Finland and Sweden said a subsea gas pipeline and telecommunications cables had been damaged, including a link between NATO members Finland and Estonia. Finland said its review of vessels in the area at the time found a Russian and a Chinese ship among them.
President Vladimir Putin has dismissed the idea Russia was involved as "rubbish;" the Chinese shipowner, NewNew Shipping, declined to comment.
The Netherlands and Denmark have both accused Russian ships of attempting to map what Sweden's Prime Minister has called a "spaghetti" of critical infrastructure in their waters.
But of the governments surveyed, only Britain and Poland said they had invested or budgeted for steps to improve the security of offshore infrastructure. The others declined to answer questions on budgetary commitments or said they were now looking into further funding.
When it comes to who should pay for such measures, most governments said the buck stops with the developers.
Britain, which has spent 65 million pounds ($79 million) adapting two vessels for underwater surveillance and seabed warfare, said its government was responsible for security policy and works with industry to implement protection measures.
Seven other countries said the job of securing energy assets falls mainly to industry, although the naval forces play a role.
Officials at two large wind energy firms and at two defence companies told Reuters only a few wind farms have installed radars to monitor traffic. Otherwise, they said, no security equipment is installed today - because there are no requirements to do so and because of the cost.
"I think it's extremely important to say that protection of assets within territorial waters is a state matter and not (that of) a developer," Orsted CEO Mads Nipper told Reuters in April.
Orsted has 12 operating wind farms in the UK, five in Denmark, four in Germany, and one in the Netherlands.
Soaring inflation and interest rates, increased seabed leasing fees and volatile energy markets have all come together to squeeze European wind developers in the last two years.
In March, NATO set up a unit to address vulnerabilities of undersea infrastructure: it says it has boosted ships and aircraft patrolling the Baltic and North Sea.
The threat is acute. Swedish Rear Admiral Ewa Skoog Haslum has called the situation at sea "very intense" and James Appathurai, NATO's Deputy Assistant Secretary General for Emerging Security Challenges, told a conference in Copenhagen earlier this month the threat is a live one.
He said Russia's Undersea Research Program has spent decades mapping out Europe's critical undersea infrastructure and "preparing ways to sabotage it".
"It's extremely well resourced," he said. "These are very, very modern ships with very, very modern capabilities, including remotely operated vehicles that come out from underneath."
Moscow did not respond to a request for comment.
Individual turbines are not as critical as infrastructure such as high-voltage cables, Apparuthai and six industry sources said.
Solutions include underwater drones to monitor subsea infrastructure, small radars and cameras to observe ships, and sensors inside power cables to detect unusual movements.
Installing such equipment on a large wind farm would cost between 20 million euros and 60 million euros ($21 million-$63 million), according to three industry sources. Overall cost data is not widely available but as an indication, that would be less than 2% of the cost of one project, Sofia, being built by Germany's RWE in the North Sea.
If North Sea countries were to meet their target for extra offshore capacity, that would cost up to 3.6 billion euros more to secure, according to Reuters calculations. Surveillance including active patrols would add much more.
Under the European Union's Internal Security Fund for 2021 to 2027, 1.35 billion euros are available for members to increase security in their countries, said the European Commission's spokesperson for home affairs, Anitta Hipper. This may be spent on critical infrastructure, but that's up to individual countries, she said.
An EU directive that focuses on strengthening resilience of critical infrastructure came into force this year. It requires every country to have plans in place to protect their critical assets by 2026.
Military officials, lawmakers, and the wind industry in at least five countries have yet to agree who should bear the cost, nine wind and defence industry insiders and government officials told Reuters.
Finland, Sweden, Denmark, the Netherlands and Germany either told Reuters or have said elsewhere that it is primarily industry's responsibility to invest and secure wind farms; Poland and Belgium have said it was a shared responsibility and the other countries said the state or navy should have a role to play in risk assessment or in threat situations.
Norway, Estonia, France and Lithuania did not respond to Reuters' inquiry. Latvia has yet to build its planned windfarms, so declined to comment.
"Protecting underwater infrastructure, including cables, pipelines and wind turbines, is crucial but challenging. It requires a lot of effort from the government side," said Mattia Cecchinato, senior adviser for offshore wind at WindEurope.
"The industry wants to and must do its part too."
'SOMEONE TAKE CHARGE'
A direct attack on a NATO country could trigger a full response from the alliance. NATO is clear that within territorial waters, it's down to states to protect their infrastructure.
But without surveillance, it is not possible to find culprits. And most planned new offshore projects will be in international waters.
There is one planned project where Orsted says the roles are clear - a 1.5 gigawatt offshore wind project it is building in the Polish part of the Baltic.
Poland in July passed legislation to allow its military to sink an enemy ship targeting energy infrastructure there. It said it would establish a permanent coast guard base close to where offshore wind farms are planned.
"It is very clear in Poland who is responsible," said Orsted's head of European operations Rasmus Errboe.
But even Poland thinks the burden should be shared.
"The military's role is to defend critical infrastructure in war time ... but the day-to-day activity of protecting infrastructure is a commercial issue," said Krzysztof Jaworski, Commander of the Naval Operations Centre in the Polish Navy.
Elsewhere in Europe, Orsted's Errboe said, there are different framework conditions depending on where you are.
"From the industry's side, there is an unequivocal need for someone to take charge," he said.
($1 = 0.8235 pounds)
($1 = 0.9457 euros)
(1 euro = 0.8721 pounds)
(Reuters - Additional reporting by Benjamin Mallet in Paris, Riham Alkousaa in Berlin, Elizabeth Piper in London, Toby Sterling in Amsterdam; Andrius Sytas in Vilnius, Marek Strzelecki in Warsaw, Moscow bureau; Edited by Sara Ledwith)