Dark ships and shadow fleets – what is crossing 'closed' Strait of Hormuz?

Iran's move to shut the Strait of Hormuz has brought shipping through the 24-mile stretch of water close to a standstill.

Only a handful of vessels have transited in recent days, many switching off their tracking systems or linked to "shadow fleets".

"They can't physically close a waterway of that size, but the threat is there", said Richard Meade, editor-in-chief of maritime risk company Lloyd's List Intelligence.

Mr Meade said Iran has a proven history of using everything from ballistic missiles to unmanned aerial and seaborne drones.

What is making it through?

Sky News' Data & Forensics team has focused on 13 ships that have transited the Strait of Hormuz between 2 and 9 March.

We know the real number of crossings is much higher, as some ships turn their tracking system off, a practice known as going "dark".

Data from marine analytics firm IMF Portwatch suggests that in normal times, about 30,000 ships transit the strait per year, that's 82 per day.

The animation below shows how shipping traffic dramatically changed.

Of the ships we have identified passing through the Strait of Hormuz, many have links to Iran, China or Russia. There are also ships from Greece, India, the UAE and Singapore.

Five vessels managed by Greek firm Dynacom have transited the Strait since the war began, according to marine tracking data from Kpler.

US President Donald Trump has been urging shipowners to "show some guts" and keep sailing.

'Shadow Fleet' have crossed the most

Shadow fleet tankers dominate current crossings of the Strait of Hormuz, according to Lloyd's List Intelligence.

They found that, of the 13 large oil and gas carriers that crossed between 2-9 March, eight were classified as part of the so-called shadow fleet.

A tanker is classed as a shadow fleet if it is carrying sanctioned oil cargo from Iran, Russia or Venezuela.

What has been attacked?

Ten vessels in or near the Strait of Hormuz have been attacked since Iran blocked the waterway, according to the International Maritime Organisation (IMO).

Four vessels were attacked on 1 March, three people died that day, and multiple people were injured. Two vessels were attacked on 3 March, and at least one attack every day until 7 March.

According to United Kingdom Maritime Trade Operations (UKMTO), a total of 14 incidents from 28 February to 10 March have affected vessels operating in and around the Arabian Gulf, Strait of Hormuz and Gulf of Oman.

In the interactive map below, suspicious activity, attacks and advisories are shown.

These ships carry the flag of many different countries, including the US, Marshall Islands, Gibraltar, United Arab Emirates, Bahamas, Panama and India.

On 4 March, a Malta-flagged container ship attempted to transit the strait and was hit by a projectile as it got close to the midpoint.

Tracking shows the Safeen Prestige grinding to a halt. The attack caused a fire in the engine room, and the crew had to abandon ship.

Sky News has verified CCTV video from another attack on the same day. A US-managed ship, Sonangol Namibe, was attacked by an unmanned drone boat.

The ship was 30 nautical miles southeast of the Kuwait coast. UKMTO reported an oil spill because of the incident.

The IRGC has warned that any US, Israeli or European vessel detected in the strait "will certainly be struck".

A surge in GPS jamming

There has been a huge surge in GPS jamming in the region. Hundreds of ships jump around the map and then cluster in very small areas.

GPS ship jamming is when signals are being interrupted, causing ships to send incorrect locations.

It's impossible to know exactly who is behind the jamming but analysts say it's likely to be both from Iran and others.

While Iran is widely suspected of trying to disrupt shipping in the region, analysts say the surge in GPS jamming could also be linked to others, including vessels seeking to mask their movements or respond defensively to threats, making it difficult to attribute the interference to a single source.

How has cargo shipping changed?

The Strait of Hormuz's closure also has global implications for commercial shipping routes. The two largest companies, Maersk and Mediterranean Shipping Company (MSC), make up nearly 30% of global containerised shipping capacity in the world.

Both of these companies have suspended shipping to the Middle East.

Maersk said: "This decision has been taken as a precautionary measure to ensure the safety of our personnel and vessels."

Tracking data from MarineTraffic shows container ship 'Maersk Cincinnati' rerouting its course away from the strait.

On 2 March, the data shows the ship did an almost U-turn at around 2pm UTC. It continued to retreat from the area until 4 March, finally returning to the Port of Salalah in Oman, heading to the Gulf of Kutch on 10 March, where it appeared "laded", heavily loaded.

Mr Meade said: "We're seeing a number of ships doing U-turns. They're likely getting orders to go and perform alternative operations. Now, that's fine for the ships that are headed into the Gulf, but for the ships that are already there, they're essentially stuck."

Additional reporting by Joely Santa-Cruz, Data Journalist

The Data x Forensics team is a multi-skilled unit dedicated to providing transparent journalism from Sky News. We gather, analyse and visualise data to tell data-driven stories. We combine traditional reporting skills with advanced analysis of satellite images, social media and other open source information. Through multimedia storytelling we aim to better explain the world while also showing how our journalism is done.

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