Iran has effectively closed the Strait of Hormuz, the only maritime passage into the Gulf, which is also known as the Arabian Gulf and the Persian Gulf.
It separates Iran on one side from Oman and the United Arab Emirates on the other. In short, there is no way in or out by sea when the Strait of Hormuz is closed.
Roughly one-fifth of global oil supply passes through it, but attacks on ships have stopped nearly all tanker traffic.
NDTV's Tejshree Purandare reports from an undisclosed location in the Persian Gulf that has been disrupted by the regional war, which began with US-Israeli strikes on Iran on February 28 and has since spread across the Middle East. Further north lies the Strait of Hormuz, the very passage the reporter's vessel would have been required to transit.
More than 300 vessels are stranded in the Persian Gulf, on one side of the Strait of Hormuz and more than 700 on the Gulf of Oman, Captain Pradeep Singh, a ship owner, told NDTV.
Iran accuses Gulf states of allowing US forces to carry out attacks from their territory, and has launched missile and drone strikes against what it calls US interests in those countries throughout the war.
Gulf states have repeatedly denied those accusations, saying even before the war that they would not allow their territory or airspace to be used to attack Iran.
"If we keep going north, we will reach a place where we need to transit the Strait of Hormuz. Strait of Hormuz is a very narrow channel of 90 miles long and 20 miles in breadth and we have more than hundreds of vessels passing through every day," Captain Singh, who was on board a ship with this reporter, said.
At least 21 vessels have been hit or targeted, or have reported attacks, since the start of the war, according to an AFP news agency count on March 18.
"If you see the numbers, the larger ships which carry 100% of the world's oil are only limited in numbers, maybe 5,000 to 6,000, which is very surprising for normal people. You have almost 700 vessels stuck in this area. The whole supply chain is getting strained," he added.
In recent days, Iran has allowed a handful of vessels from countries it considers friendly to pass through the Strait of Hormuz, one of the world's great bottlenecks, while warning it would block ships from countries it says have joined the "aggression" against it.
At least 40 energy assets across the oil-and gas-exporting region have been "severely or very severely damaged" in the conflict, said International Energy Agency chief Fatih Birol, as the war ignited by Israel-US attacks on Iran entered its fourth week.
"If oil is not available, then the prices will go up. If oil is not available in this area and this conflict persists, countries will try to find solutions from different locations like Russia, Venezuela, US and North Europe," he said.
With oil prices hovering above $100 a barrel over supply fears, US President Donald Trump on Saturday threatened to "obliterate" Iranian power plants if Tehran failed to reopen the strait within 48 hours.
The ultimatum, made just a day after the US leader said he was considering "winding down" military operations, came as the critical waterway remained effectively closed.
Greenpeace warned last week that dozens of tankers carrying around 21 billion litres (5.5 billion gallons) of oil were trapped in the Persian Gulf.
"This is an ecological ticking time bomb," said Nina Noelle, of Greenpeace Germany, who has been mapping oil tankers in the region.
