They come one by one in the dead of night, when all is still apart from the crashing of the waves.
A convoy of up to 20 tankers protected by fighter jets, helicopters and ships has been ferrying up to 10 million barrels of oil out of the Gulf each night since May in a secretive US naval operation.
The US military has been leading the ships into and out of the Strait of Hormuz, but rather than taking them through the route which passes Bandar Abbas in southern Iran, the vessels instead hug the northern coast of Oman.
While the oil shipments are nowhere near pre-war levels, the covert operation, first revealed by Axios, the US news website, has been helping to keep the world’s lights on amid the war in Iran and the resulting restrictions on shipping.
About 10 million barrels of oil have been moved each day – about half the volume transported before the start of the Iran war in February.
Vessels were expected to transport 15 million barrels in just one night this week, one official said.
The task force overseeing the mission is being run out of the US army headquarters in Fort Bragg, North Carolina.
In co-ordination with regional partners, it creates a daily list of ships travelling from the Gulf into the Arabian Sea, as well as a list of empty leased tankers making the journey in the other direction to collect more oil.
During the nightly missions, the ships move in two big inbound and outbound lines.
Cargo ships queue to pass through the Strait of Hormuz despite the dangers – Amirhosein Khorgooi/ISNA/AP
Ship operators register the trips with the US military and report possible threats or attacks as they occur. They typically turn off their transponders to avoid being noticed by Tehran.
The vessels then pass through the southern channel based on US military guidance, protected from Iranian cruise missiles and drones.
The secret effort is run in conjunction with the US naval blockade of Iranian ports, which Washington established in response to Tehran’s closure of the narrow waterway.
“We have been controlling the southern lane of the Strait of Hormuz for two months now. The Islamic Revolutionary Guard Corps (IRGC) can be a nuisance, but they don’t control the strait. We do,” a US official said.
Iran has diminished visibility of the southern channel, with just a few radars and spotters in small IRGC fast boats.
The IRGC patrols the shipping lane using fast attack boats – Morteza Nikoubazl/Nur Photo/Getty
Most attacks are blind-launched drones and cruise missiles in the general direction of the ships’ transit routes.
At least 15 ships taking the southern routes have been attacked by Iran since the beginning of June, killing two ship workers and injuring 16, according to The New York Times.
A ship was struck this week while sailing near Oman, leaving one mariner dead, the United Kingdom Maritime Trade Operations reported on Tuesday.
Some attacks have also been thwarted by Washington. Earlier this week, US forces shot down eight Iranian drones and two cruise missiles.
But the protection has come at a cost, using up vital resources to ensure safe passage.
More than 1,000 ships have crossed the strait through the new channel, according to US Central Command.
Yet this remains far below the pre-war traffic levels, when American resources were not needed to keep global oil supplies moving.
Some larger shipping companies remain deterred by the threat of Iranian attacks, which have also targeted oil and gas facilities in Gulf states.
An ever-defiant Donald Trump told Axios on Wednesday that there was “a tremendous amount of oil coming out of the Strait of Hormuz”.
But with the US president dismissing negotiations with Iran as a “waste of time”, the world can only rely on his naval operation to keep the oil flowing.