The US and Iran signed a ceasefire framework last week that includes reopening the Strait of Hormuz, but shipping companies and insurers have cautioned that the waterway remains hazardous.
The main reason is naval mines. Under the agreement’s terms, Iran is required to clear any mines within 30 days, with France and the United Kingdom leading demining operations supported by Germany, Italy, Japan, and Canada.
Naval mines are underwater explosives designed to damage or sink vessels. They are cheap to manufacture but expensive and time-consuming to find and remove. Four main types are deployed in contested waterways.
Bottom mines sit on the seabed in shallow coastal waters and straits, detonating when a ship passes overhead by detecting its magnetic, acoustic, or pressure signature.
They are difficult to spot because they can resemble rocks or debris on sonar screens. Moored mines are tethered to the seabed by cables and float near the surface, the classic image from wartime photographs.
They detonate on contact or through proximity sensors. Drifting mines are unattached and move with currents, making them the hardest to contain – they can travel far from the original conflict zone and threaten commercial shipping lanes. Limpet mines are smaller devices attached directly to a ship’s hull using magnets or clamps, with a timed detonator.
Clearing mines, formally called mine countermeasures, follows two approaches. In hunting, ships deploy sonar-equipped underwater drones and remotely operated vehicles to scan the seabed. Once a suspected mine is identified – distinguishing it from the rocks and wreckage that fill the screens – operators either detonate it in place or disable it using specialist divers or robotic vehicles.
In sweeping, ships tow cables fitted with cutters that snag the mooring lines of tethered mines and release them to the surface for safe destruction. Other vessels tow equipment that mimics the magnetic and acoustic signatures of ships, tricking pressure-sensitive mines into detonating early.
The process takes time for a straightforward reason. Locating a single mine is hard. Proving that an entire corridor contains none is harder still. A single confirmed mine is enough to close a shipping lane entirely, and even rumours of mines push insurance premiums higher and slow cargo traffic. The tankers and container ships transiting Hormuz can be worth hundreds of millions of dollars, with insurance costs that may exceed that figure.
Reuters reported that demining operations in the strait could take weeks beyond any formal reopening agreement, as each shipping lane must be swept multiple times before insurers and shipping firms are satisfied it is safe to transit.
