A small Pacific nation was cast into the global spotlight when the suspected Russian "shadow vessel" Eagle S dragged its anchor across undersea cables in the Gulf of Finland in 2024.
The ship — which severed the power and internet cables between Finland and Estonia in what was thought to be sabotage — was registered in Cook Islands.
The incident followed a period of rapid growth in the number of Cook Islands-flagged ships, many of them Russian "shadow vessels", according to research organisations.
It was one of several Pacific countries named in reports identifying nations flagging "shadow fleet" vessels — ships engaging in deceptive shipping practices, lacking Western insurance and whose ultimate owners are unclear.
The shadow fleet expanded after Western nations imposed a price cap on Russia's oil following its invasion of Ukraine, and shadow vessels have shipped sanctioned oil.
Under international law, commercial ships must be registered to a country, and the shadow vessels took on the flags of nations open to registering overseas tankers — often called "flags of convenience".
"That's where the Pacific Island nations have entered the picture," said Elisabeth Braw, a senior fellow at the Atlantic Council, a United States think tank.
Many vessels joined the registries of Pacific nations that had little expertise in international fleets, she said.
"Every country has the right to flag vessels. There's no rule in the world that says you have to have maritime expertise in order to be able to flag vessels," Ms Braw said.
But Pacific Island registry administrators say they are now de-flagging ships sanctioned by Western nations, while tightening their own regulations.
Observers say Pacific Island countries make relatively little revenue from their registries, and are realising that flagging shadow vessels comes at a cost.
"Small states now appreciate that association with sanctions evasion networks threatens their credibility, external relationships, and participation in the Western-led maritime order," said Basil Germond, a professor of international security at Lancaster University in the United Kingdom.
Out of the shadows
There are more than 1,900 shadow vessels globally — an estimated 10 per cent of all tankers worldwide, according to maritime intelligence firm Windward.
Revenue from shadow vessel oil shipments helps Russia sustain its illegal invasion of Ukraine.
By 2024, reports found Cook Islands and Palau, another Pacific nation, had some of the fastest-growing shipping registries flagging shadow vessels.
S&P Global reported a large increase in Cook Islands and Palau-flagged vessels with characteristics common in the shadow fleet, while the Centre for Research on Energy and Clear Air in 2025 named the countries in a list of the top 10 fastest-growing shipping registries for Russian shadow vessels.
Last year, a report from Ukrainian think tank the Kyiv School of Economics also found Vanuatu had begun flagging shadow vessels carrying Russian oil since August 2025.
Observers say the vessels have been attracted to Pacific Island registries for their limited capacity to enforce regulations, and because they offer quick and low-cost registration.
It was also common for nations — including in the Pacific — to let private operators based in other countries manage their registries, said Eduardo Cavalcanti de Mello Filho, a researcher on international law of the sea at University College London.
"However, it means that commercial incentives may influence registry growth strategies," he said.
As Pacific nations expanded their shipping registries, it was the Eagle S incident that brought them to world attention.
Finnish police and coastguard officials boarded the Cook Islands-registered vessel and brought it to a location near a Finnish port where crew members were questioned.
A Helsinki court in October last year found it lacked jurisdiction over the matter, saying this lay instead with Cook Islands as the vessel's flag state, or in the defendants' countries of nationality.
The court classified the case as an "incident of navigation", saying prosecutors had failed to provide sufficient evidence to show the crew dragged the anchor intentionally, according to news wire agency Reuters.
John Hosking, secretary of Cook Islands' Ministry of Transport, said the country deregistered the Eagle S — now under EU sanctions — on October 16.
The nation's shipping registry administrator had concluded a technical investigation into the cause of the vessel's anchor loss, he said.
"We are currently finalising the formal report and identifying key lessons learned this month, with a safety notice expected to be released to the maritime community in early March 2026," he said.
A shrinking registry
Like other Pacific Island nations, Cook Islands says it is removing Western-sanctioned vessels from its registries.
Mr Hosking said Maritime Cook Islands (MCI), a private company that administers the country's registry, had removed nearly 190 of the 214 tankers registered since 2022.
Of these, it removed 53 vessels due to sanctions and 135 for not complying with MCI directives or for using insurers that no longer met its vetting criteria.
"Any vessel identified as being subject to international sanctions is promptly deleted from the register within seven days of being named," Mr Hosking said.
"MCI implemented a prohibition on Cook Islands-flagged vessels operating in the Baltic Sea, as well as a ban on vessels carrying Russian, Iranian, or Venezuelan petroleum products."
He said Cook Islands and its agencies "categorically reject assertions that the registry hosts or facilitates a sanctioned dark fleet".
It also monitored its flagged vessels to identify suspicious activity and had mandated their use of MCI-approved insurers, Mr Hosking said.
"These enforcement changes are driven by our own mandate to protect the sovereignty and reputation of the Cook Islands," he said.
"The recent contraction of the registry is a direct reflection of this proactive stance."
Palau recently ended its arrangement with its private shipping registry operator, but had already deregistered "shadow fleet" tankers before the decision, Mr Cavalcanti from University College London said.
William H Moses, director of Palau's Bureau of Marine Transportation, said the government screened vessels against known sanction lists and other credible sources of information.
He said the Palau government intended to enhance oversight of the registry, and was monitoring selected ship types for prohibited activities.
"We consider our vetting process to be robust and we will continue to use [them] while we give more attention to suspect vessels," he said.
Vanuatu Logistics and Administrative Services Limited, the New York-based administrator of Vanuatu's shipping registry, said it updated its sanctions policy in October to apply European Union and UK sanctions in addition to UN and US listings.
Saade Makhlouf, the company's president and CEO, said the registry conducted a recent fleet-wide review identifying four vessels that raised "sanctions-related concerns" under its expanded screening criteria.
"Those vessels were subsequently deleted from the registry," he said.
Vessels using 'false flags' target the Pacific
Experts say the move among Pacific nations to de-flag vessels showed they had listened to Western nations discouraging them from registering shadow tankers — particularly those under sanctions.
"There's generally a receptiveness for this argument on the side of flag states," said Benjamin Hilgenstock, head of macroeconomic research and strategy at the Kyiv School of Economics.
However, shadow vessels could still look to register in other countries that previously had no role in international shipping, he said.
"These jurisdictions may be in the Pacific Ocean, but very often they're in sub-Saharan Africa," Mr Hilgenstock said.
"Where exactly this is heading is a little difficult to predict."
With fewer nations willing to let the tankers onto their registries due to Western political pressure, more vessels are using "false flags", experts say.
In some cases, vessels have claimed to belong to Timor-Leste through a fraudulent shipping registry, and to Tonga, which closed its international shipping registry in 2002.
Cook Islands and Vanuatu have reportedly warned that vessels have falsely used their flags.
Vessels also continued to "hop" between permissive or weakly governed registries willing to flag them, said Professor Germond, from Lancaster University.
He said "naming and shaming" remained the clearest deterrent against nations flagging shadow vessels.
Regional partners of Pacific nations must publicise and identify the flags of vessels engaged in deceptive or sanctioned activities, he said.
"Crackdowns have increased freight, insurance, and compliance costs, extended travel routes, and pushed operators toward aging hulls and non-Western services," Professor Germond said.
"But the shadow fleet remains resilient."
