Shipping was a murky world, now it's gone 'dark' to cross the Strait of Hormuz

Marine traffic observers have revealed hundreds of commercial ships have crossed out of the Strait of Hormuz, often by taking "dark" journeys through Iran's "toll-booth route" or with the guidance of the United States.

Analysts also say some Iranian tankers are likely slipping past the US blockade in the opposite direction and entering Iranian waters to be used to store oil offshore.

With new strikes across the region in recent days, any progress on opening the Strait of Hormuz via negotiation has been plunged into uncertainty.

But in the weeks since the United States-Iran ceasefire was announced and American warships moved into the Gulf of Oman to enforce a blockade on Iranian ports, some vessels have been sailing in and out of the crucial waterway without their marine tracking transponders switched on.

The numbers are still far below typical pre-war traffic levels, when up to 140 commercial vessels crossed the strait each day, but all prominent marine intelligence organisations are reporting a level of activity.

Marine intelligence company Windward has been monitoring traffic via satellite and told the ABC it has observed more than 80 commercial ships crossing the Strait of Hormuz and leaving the Persian Gulf in the last five weeks.

These vessels transited either by negotiating safe passage with Iran with support from US forces.

"We believe that most — but not all — dark transits that have occurred have been with the knowledge and permission of Iran via diplomatic level negotiations," Windward analyst Michelle Bockmann said.

Windward is watching each vessel that crosses out of the Strait of Hormuz and adding it to the tally once it has made it to the Arabian Sea and left the area, indicating it is genuinely making an onward journey.

Ms Bockmann noted nearly 40 "dark transits" had taken place in the strait between March 1 and May 7, in the weeks following the outbreak of the war.

Each marine tracking organisation has different parameters for how it is quantifying traffic around the Strait of Hormuz, including what type of vessel is included and where the vessels go once they cross.

Lloyd's List, another monitor, estimates nearly 40 formerly stranded, non-Iranian vessels exited the Persian Gulf in the three weeks until June 3, bringing total departures since March to 142.

Another marine intelligence company, Kpler, recorded a much higher number of crossings and told the ABC 264 ships had exited Persian Gulf since the start of the ceasefire until early June.

Out of those, 22 were Iranian-flagged and half of those Iranian ships were part of the dark fleet.

This traffic has been making its way across the Strait of Hormuz to exit the Persian Gulf, but some empty Iranian tankers have been making their way in despite US warships patrolling the Gulf of Oman, according to analysts.

The strait's significance has been in the spotlight since Iran placed an effective chokehold on the shipping route used for 20 per cent of the world's oil and gas trade, as well as one third of the global fertiliser supply, before the outbreak of war.

Tehran had been preparing for a conflict in the region and was ready to weaponise the crucial trade route.

New strikes between Iran and Israel come amid ongoing and increasingly bold attempts by the regime to formalise its control over the Strait of Hormuz.

Analysts say that may not have been in the regime's original war strategy, but now gives Tehran an edge.

How ships exit the Persian Gulf

International Crisis Group analyst Christopher Newton has looked at the evolution of the role of the Strait of Hormuz since the war began.

"The strait is partially open as, essentially, it's been the entire war," he said.

"Both Iran and the US want certain traffic through that they approve of on their own terms, more than either one of them has ever wanted to fully close it off."

Most of the ships in the strait are "being dark", which Ms Bockmann says is occurring largely for security reasons, to evade blockades, and to avoid being caught engaging in Iran's "toll-like" system.

"Another reason for going dark of course is to avoid secondary sanctions exposure or claims that they've paid a toll to transit," she added.

"You sort of see their signal as they come to the Gulf of Oman, they go dark and then they resume like 10 or 13 days later because they've gone in dark, they've loaded dark, and come back."

While ships that are exiting the strait are not advertising that they have negotiated any terms to exit with the Islamic Revolutionary Guards Corps (IRGC), it is widely reported that Iran's establishment of the Persian Gulf Strait Authority (PGSA) has given a way for stranded ships to gain permission to exit after months of waiting for the war to end.

"It is largely posturing by Iran and also helping Asian countries satisfy their domestic political agendas, because obviously there's an oil shortage there," Ms Bockmann said.

She said ships exiting was not an indication of "sustained increased traffic", but rather a "signal that Iran is prepared to negotiate and make bilateral agreements".

Pakistan, India, Iraq and Malaysia are some of the countries reportedly involved in direct talks with Tehran, coordinating vessel transits via the IRGC's new vetting system.

Mr Newton agreed Iran's "friends" were striking agreements and exiting the strait.

He said that initially it was ships affiliated with Iran's friends taking the regime-approved route out of the Persian Gulf, "but then you also get ships affiliated with US allies like Japan".

Ms Bockmann said she had also observed ships with Western links leaving the Persian Gulf.

"There has been a small cohort, many with perceived US or Israeli ties that we believe have exited the strait with their AIS off, likely without [IRGC] permission," she said.

Reports of the number of ships being guided out of the Persian Gulf by American forces vary greatly, but about a week ago the New York Times reported that US Central Command had helped about 70 commercial ships through.

There are two routes being primarily used by some ships exiting the strait: a northern corridor and a southern corridor.

Depending on which ship used which route, it is possible to hazard a guess as to whether the ship left with permission from Iranian or US forces.

Those with permission from the IRGC are more likely to use the northern corridor, with Iran's preferred route swinging around Larak Island – north of the waterway. This has come to be known as Tehran's "toll booth route".

"It was just one lane for inbound and outbound traffic involving a toll for at least some oil tankers," Mr Newton said.

In recent weeks that route has expanded.

"No-one on the outside can say if a toll was paid or not … but if they are swinging north of the official TSS (Traffic Separation Scheme) then it likely involved Tehran's approval," Mr Newton said.

The TSS is the shipping lane system used before the war and accepted by the International Maritime Organisation.

The other route noted by the two analysts is the southern corridor.

"Essentially, ships hug the Omani coast as tightly as they can, depending on the ship and water that's deep enough," Mr Newton said.

Ms Bockmann said it was "a safer alternative", because the US believed there was a lack of mines closer to the Omani coast.

Project Freedom, the US operation to guide ships through the strait had proposed to use the southern corridor.

Project Freedom was halted just days after it was announced by the US President.

Mr Newton said the US had a route to help ships exit the strait, but the planning was not comparable to Iran's PGSA.

"On the Iran side, they're very clear. They want the formality," he said.

"They want to give you the GPS coordinates. They want it to be as formal-looking as it can."

At the same time, where the US project failed to gain confidence in the area, Iran's approach to a new passage system appears to be working.

"You've got major shipowners now publicly saying, you know what, $200,000 a pop is pretty reasonable for not dealing with the hassle of drones and missiles,"

Mr Newton said.

Greek shipping mogul Evangelos Marinakis suggested that paying a fee for passage through the strait was preferred to no transit at all.

"Even if we had to pay a fee, for me [it would] be much better than to have the straits closed," he said at the TradeWinds shipping conference in Athens last week.

According to Mr Newton, these sort of statements are a concern for the US.

"It's the growing list of countries deep within the US orbit by treaty or by their actions that appear willing or at least compelled to use Iran's alternative arrangements," he said.

In a data visualisation posted by the PGSA to X, the body said 12 per cent of applications to exit the Persian Gulf came from Europe-affiliated ships.

The state of the Strait of Hormuz

For more than three months Iran's long-held plan to control the Strait of Hormuz has been in action.

As the ABC has previously reported, there were divisions in the regime over the decision not to move on the strait during last year's 12-day war. This time, the IRGC moved quickly to seize control.

But its approach to the strait has been changing throughout this war.

What started as a military operation to push traffic out of the strait with force and shut down the trade route, has now evolved.

Iran is accused of firing explosive drones towards ships in the strait in recent days, but the operation over the waterway has also involved attempts at running the PGSA to charge administrative fees and a diplomatic exercise with Oman.

Iran has been negotiating with Oman — its only coastal partner on the Strait of Hormuz — to establish an administration over the waterway.

There are options to do this legally, but international law also says coastal states cannot hinder safe passage.

"They have been making military arrangements to control the Strait of Hormuz for years, at least 10 years, and they had been conducting military drills with IRGC, [and a] very small contribution by the National Navy," Washington Institute senior fellow Farzin Nadimi said.

The Iranian military capacity expert said the IRGC practised taking the strait by aggression "numerous times", but he did not believe there had been any previous plans to come to a political arrangement with Oman.

"I don't think they ever reached that stage … to come up with actual plans. I think whatever we are seeing [now are] just makeshift arrangements," he said.

Internally, the Iranian parliament is reviewing legislation designed to bring the strait under state control.

This week Iranian envoy to Moscow, Kazem Jalali was quoted as saying: "Of course this strait will be open, but with new conditions to be determined by the Iranian and Omani authorities."

"We understand that Iran and Oman provide certain services related to this strait. And fees will be charged for those services," he said.

There is reporting of tolls being charged for Iranian approval to cross the strait. The regime says these are likely to be in the form of environmental fees, but the nature and perhaps even the amount of these charges are beside the point, according to Mr Newton.

"This is so much more than just a revenue grab,"

he said.

"We're coming to the point where some people, to get their ships through, to get their exports out, might be quite happy to pay a certain size toll,

"And Iran could still say no because of its political objectives, because that is a more a demonstration of power than always just saying yes and taking everyone's money," he said.

Weeks ago Iran published maps indicating the area its armed forces would be patrolling and controlling extended to the Omani coast, now the regime wants a formal arrangement with its coastal neighbour.

Mr Nadimi believed the Iranians were not satisfied with their progress.

"I can see frustration in Iranian language and probably that comes from the fact that Omanis are not very cooperative. They say that talks are ongoing and they are talking with Omanis to come up with this kind of system, but I don't think it is going to work," he said.

Iran and US in 'deadlock'

It does not appear to be monetary value Iran aims to gain from its push to regulate the Strait of Hormuz.

"The value of some of the tolls that Iran or bodies linked to the Iranian government have publicly floated are usually dwarfed by the value of things like broad US sanctions relief," Mr Newton said.

"They're threatening things like tolls that are very disruptive, but, in terms of the financial value to Iran, are not nearly as significant as what they're trying to get in negotiations."

Sanctions prevent much of the world from really engaging with bodies like the PGSA.

"It really is kind of the single greatest barrier, because there's sanctions across various different countries, the US, UK, Canada, Australia, EU, and also terrorist-financing laws that are significant," Obsidian Risk Advisors sanctions specialist Brett Erickson said.

"You'd have, potentially, the individual who owns the company or who is operating the vessel, they would be personally sanctioned."

Mr Newton said from the Iranian perspective the Strait of Hormuz represented power.

"Iran is holding that power because Iran is the one that has disrupted shipping and the US is the one that has failed to prevent the disruption,"

he said.

The US blockade is in position in the Gulf of Oman to stop Iran shipping oil from its ports, but Mr Newton says empty Iranians tankers have made their way past.

"[Iran is] getting very clever with storage. It keeps getting empty tankers through the US blockade. Each one of them could be more than a day's worth of oil exports at this point," he said, referring to how storing oil offshore allowed Iran to keep up production levels.

But if there is to be progress on the strait, there needs to be a break in the "clear deadlock for both sides", according to Mr Nadimi.

"This is not obviously sustainable and both sides know that," he said.

Mr Nadimi said Iranians had some time to play with.

"They have been monitoring the domestic temperature … whether the society is going to revolt against the economic conditions, but they haven't been seeing any worrying signs yet," he said.

The official, negotiated future of the Strait of Hormuz is a sticking point between US and Iranian delegates attempting to end the war.

Unofficially though, some ships and their crews have been able to find a way through.