Last spring, the Grace I left a filling station in the middle of the Persian Gulf loaded down with 2.1 million barrels of Iranian crude. Too large for the Suez Canal, the oil tanker made the long journey around the coast of Africa before showing up at the mouth of the Mediterranean Sea last month.

British authorities in Gibraltar impounded the ship and its cargo on suspicion it planned to deliver the oil it was carrying to Syria, which would violate EU sanctions against the country. Iran quickly retaliated and seized a British tanker in the Persian Gulf on a trumped-up charge.

After six weeks in maritime purgatory, the Grace was eventually allowed to depart, on the assurance that it was not headed for Syria. But some experts are convinced that's not true.

Giorgos Beleris, oil research manager at data firm Refinitiv, says only three countries at the moment are willing to accept Iranian oil: Turkey, Syria and China. "It was bound to head to one of them," he said in an interview.

After Grace I was impounded by British authorities in Gibraltar, the Iranians seized a British tanker, the Stena Impero, shown here being surrounded by Iranian warships in the Persian Gulf in July. (The Associated Press)

U.S. authorities sought the seizure of the vessel while it was still under Gibraltar's control, but the ship left before the Americans could step in and intercept it.

On Aug. 18, the tanker changed its name from the Grace I to the Adrian Darya-I and changed its flag from that of Panama's to Iran's. It set a course eastwards away from Gibraltar, claiming its destination was Kalamata, Greece, a place where the type of oil it's used to off-loading comes from olives, not crude.

Grace I changed its name to the Adrian Darya-1 shortly after being released from British custody in the waters off Gibraltar. In this photo, a crewman is seen taking a picture of the vessel's new signage. The old name can be seen painted over underneath. (Jon Nazca/Reuters)

If the name change weren't enough the Greek trajectory raised a few more eyebrows because — full to the gills, the way it is — the Adrian Darya is too deep and large to come into a berth in Kalamata. Even if the ship could manage it, the port doesn't even have any crude-processing facilities to off-load it with.

But the ship kept up that charade for a few days, heading east toward Sicily. Then on Aug. 23, it updated its destination to the port of Mersin, a Turkish port that's less than 200 kilometres from the Syrian border. Mersin's proximity to a refinery in Baniyas, Syria, made international tensions ratchet up that much more.

The ship continues to befuddle maritime observers by being cagey about its true intentions. And international attention on the rogue supertanker has hit an uncharacteristic fever pitch in the normally staid world of global shipping.

The United States has put sanctions on Iranian crude while the European Union has sanctions on Syria. So trying to sneak $130 million US worth of oil between the two countries would be one of the most treacherous routes to complete in the world at the moment. But the Adrian Darya's behaviour suggests the ship is hell-bent on trying.

"For sure, they are going to deliver this oil to Syria," author and defence analyst Babak Taghvaee says. Ostracized by the international community, Syria needs crude oil to keep its repressive regime in power, and the only country willing to make any effort to help that happen is Russia.

So listing a destination in Turkey is no accident, because Turkish and Syrian waters are within the sphere of influence of the Russian navy via their naval base in Tartus on the Syrian coast.

"They just want to be close enough to … Syria to gain some protection from Russian navy ships, which are in Tartus or sailing in the Eastern Mediterranean Sea," Taghvaee says.

The ship faces another conundrum in that because it is fully loaded with oil, it sits too low in the water to get through the Suez Canal. If it can't find a willing buyer, doubling back to the Atlantic would be too treacherous given the scrutiny around Gibraltar. But at 22-metres deep, it can't go through the 21-metre deep Suez until it lightens its load. So it is effectively trapped in the Mediterranean until something changes.

U.S. authorities are convinced the Adrian Darya is trying to violate sanctions on shipping oil out of Iran and into Syria. (Marcelo del Pozo/Bloomberg)

There are 2 choices

Many experts suspect the ship's plan is to meet up with an empty Iranian tanker and off-load enough of its cargo at sea in a ship-to-ship transfer in order to allow it to have a small enough draught to pass through the Suez. Plus, spreading the cargo of crude across two ships increases the odds of some of it making it to its final destination. This is exactly what Beleris thinks will happen.

"Realistically, there's two choices," he said in an interview. "Either off-load it somewhere onshore in Turkey or Syria, or put part of the cargo into another tanker, and perhaps both of them will deliver it." Failing that, both tankers will likely try to cross through the neutral waters of the Suez back to Iran and come up with another plan. "Because nobody else is taking Iranian crude," he says.

If a second tanker is indeed the plan, he expects the ship will soon turn off its transponder to try to hide its position. "It's probably going to disappear soon, I think," he said.

Some shipping observers think they may have already spotted the ideal candidate for such a ship-to-ship transfer. Ship monitoring firm TankerTrackers.com noticed another Iranian tanker, the Argo, has begun to move briskly up through the Red Sea and into the Suez Canal. It's currently loaded down with 700,000 barrels of its own oil, but once those can be off-loaded somewhere, it should be in an ideal position to meet up with the Adrian Darya in the waters north of Port Said, Egypt, where the Suez Canal flows into the Mediterranean.

Once the STS transfer has been completed and the AD1 continues southbound via the Suez, there is an increased likelihood that the IRGC may release the UK-flagged & Swedish-owned STENA IMPERO. An empty Aframax (max 730K barrels) is already sailing back to Iran from Syria: ARGO. <a href="https://t.co/qco4ZkbS5E">pic.twitter.com/qco4ZkbS5E</a> —@TankerTrackers

A new-found status

Iran, for its part, insists that there's nothing fishy going on, and says the oil has in fact already been sold to an unnamed mystery buyer. "The Islamic Republic of Iran has sold the oil of this ship, and now the owner and purchaser of this oil will decide the destination of the cargo," government spokesperson Ali Rabiei told Reuters on Monday.

Perhaps as evidence of that, the ship updated its destination from Mersin to "for order" on Monday, an indication that it claims to be available on commission to anyone wishing to hire it.

Despite its new-found status as an alleged free agent, the ship made a visible northward turn on Tuesday and seems headed towards Turkey and Syria, as some suspected.

The U.S., meanwhile, is having none of this. National Security Adviser John Bolton, who has long held animosity for the Iranian regime, said Monday it would be "all hands on deck" as the U.S. works to seize the vessel, which he said "must not be allowed off-loaded in port or at sea."

All hands on deck in the campaign to stop Iran from funding terror, destabilizing the globe, and breaking international sanctions. The illicit oil heading to Turkey on the Adrian Darya 1 must not be allowed off-loaded in port or at sea. —@AmbJohnBolton

If something fishy is going on, it wouldn't be the first time that Iran has tried subterfuge to get its crude to a willing buyer. CBC News reported last fall on Tehran's attempts at using ghost ships — tankers with their GPS transponders turned off, making them harder to track — after Washington slapped sanctions on the country's oil.

But the circuitous route of the Adrian Darya is a step beyond even that. While there's nothing necessarily suspicious about a ship changing its name, even the vessel's chosen moniker seems designed to thumb its nose at its U.S. critics.

In Farsi, Adrian Darya loosely translates as "Hadrian's Sea" — a possible nod to the Roman Emperor Hadrian who famously built a wall in northern Britain to keep out Celtic invaders from the empire he had built, which stretched from Persia to Great Britain.

Naming the ship was a nod to the man who built a "wall that protected Iran's interests against Britain and was one of the best names to be given to this giant oil tanker after its victory over the West," Iranian state-run Fars news agency was quoted as saying.

Maritime monitoring service MarineTraffic.com has called the ship "the most tracked ship in the world right now," with 21,000 online viewings of their live map of the vessel on Monday alone.

Under normal circumstances, changing a ship's name mid-journey could be an attempt to "take off some of the heat off," as Beleris puts it.

But given the heat of the intense gaze the world has cast on the ship since then, "I guess it didn't work very well."