Midget subs and kamikaze drone boats - how Iran can block the Strait of Hormuz

The fear of mines laid by submarines, kamikaze drone boats and GPS jamming have effectively closed the Strait of Hormuz.

Iran has long threatened to shut the narrow waterway through which 20% of the world's oil supplies passes, knowing that doing so would cause market havoc and send prices soaring. This is effectively what has now happened.

At least 16 ships have been hit by Iran since the conflict began, with Tehran releasing a video (below) of what it claims is the moment an oil tanker was attacked off the coast of Iraq - with devastating consequences. Now, 3,000 ships and around 20,000 crew are trapped or affected in the region, the International Maritime Organisation says.

So what tools and weapons is Iran employing in its blockade of the crucial trade route - and what is it holding back for later? Sea drones The threat of sea drones has long been a feature of the war in Ukraine, and the tactic is now being used in the Persian Gulf. Sea drones, sometimes called USVs (unmanned surface vehicles), are small, unmanned vessels that operate on or below the water's surface, making them difficult to defend against, particularly at night.

In January last year, footage released by the Iran's Islamic Revolutionary Guard Corps (below) purportedly shows such craft in an underground tunnel. Naval drones laden with explosives have reportedly been used in at least two attacks on oil tankers in the region since the war began.

Follow live: Iran war latest On 1 March, a crude oil tanker was hit 44 miles off the coast of Oman, killing one crew member. Days later, the Bahamas-flagged crude oil tanker Sonangol Namibe was hit near an Iraq's Khor al Zubair port.

Video posted online shows what resembles a naval drone slamming into the side of the ship, triggering an explosion that sent plumes of smoke into the sky. Alicja Hagopian with Sky News' data and forensics team reports that Iran has attacked at least 16 vessels around the Strait of Hormuz and the wider Gulf.

Six ships are reported to have been struck since early Wednesday alone, the most intense period of naval strikes by Iran so far. Iran has also suffered significant casualties at sea, with reports of 87 deaths after the US sunk an Iranian warship off the coast of Sri Lanka last week.

Meanwhile, Iranian UAVs (unmanned aerial vehicles), or flying drones, have also been seen. Dr Sidharth Kaushal from the RUSI thinktank told Sky News that they may pose a lower risk to the actual ships, but are a danger to their crews and have a psychological impact.

Is Iran deploying mines in the Strait of Hormuz? The possibility of Iran deploying anti-ship mines to the Strait of Hormuz has come increasingly into the spotlight as the war has continued. Made infamous through their use in huge minefields in the Second World War, these weapons would pose a grave threat to ships passing through contested waters.

Iran has some "contact mines.