Limpet Mines Return to Strait of Hormuz as Tanker Attack Escalates Threat

Two limpet mines attached to a tanker's hull exploded in the Strait of Hormuz on October 29, starting an engine room fire and temporarily disabling the vessel — the first reported success for the tactic against merchant shipping in the waterway since the conflict began on February 28. The United Kingdom Maritime Trade Operations (UKMTO) verified the incident under Warning 187-26, locating it roughly 25 nautical miles northeast of Khasab, Oman, as the tanker transited outbound from the strait.

A small boat approached the tanker's port side and attached two explosive devices above the waterline, according to UKMTO. The blasts ignited a fire in the engine room and left the ship temporarily disabled. By Friday, UKMTO confirmed the crew was safe, the fire extinguished and no environmental damage recorded. The tanker has resumed its voyage.

Why the return of limpet mines matters

Martin Kelly, Head of Advisory at EOS Risk Group, identified the vessel as the LOUISE 1 and framed the attack as another step in Iran's evolving campaign against commercial shipping. He noted that Iran last used limpet mines against merchant shipping in May 2019, when four vessels anchored off Fujairah were hit, followed by attacks on the tankers KOKUKA COURAGEOUS and FRONT ALTAIR in the Gulf of Oman in June of that year.

For operators, the concern is not the device itself but where the next one might land. Kelly warned that the implications are most serious for vessels waiting at anchor, where explosives could be placed below the waterline without the crew detecting them.

"A limpet mine below the waterline will cause significant damage and water ingress," he said.

That is a materially different risk profile from the missile and drone strikes that have dominated this conflict. A projectile gives warning on radar; a diver or small boat placing a charge on a stationary hull may not.

What else happened on Thursday?

The limpet-mine attack was one of several maritime security incidents reported in the strait that day:

• A company security officer reported another tanker struck by an unidentified projectile at approximately 1600 UTC while completing an outbound transit. No crew injuries or environmental impact were reported.
• UKMTO reported a vessel on fire roughly nine nautical miles north of Khasab. Regional authorities identified it as a dhow involved in a security incident; it caught fire, listed and sank, and its crew was evacuated safely.
• Iran's Islamic Revolutionary Guard Corps Navy claimed Friday that three oil tankers caught fire and exploded while attempting what it called unauthorized transit routes, including one tanker carrying approximately 2 million barrels of crude that it said struck a mine.

Treat that last claim carefully. Reuters, citing Iranian state media, said it could not independently verify the claims. Iran has repeatedly described attacks on ships using routes outside its control as mine strikes, yet independent evidence supporting its broader claims of sea mines has remained limited. No connection has been established between Thursday's dhow sinking and an earlier U.S. military operation that destroyed a dhow suspected of providing intelligence to Iran.

How exposed is the southern route?

The attacks are concentrating on the corridor the United States set up to keep shipping moving. Washington continues to coordinate commercial vessel movements through the strait via a southern route designed to bypass Iranian threats, but UKMTO's October 30 weekly security overview shows 59 of 81 reported projectile strikes since July 6 — nearly three-quarters — occurred along that route.

The verified record is also incomplete by design. "UKMTO reports only incidents verified through primary sources; additional incidents are known but cannot be independently verified," the agency said. That caveat cuts both ways: the true count is almost certainly higher than the official one.

Since the conflict began on February 28, UKMTO has recorded 145 Iran-U.S. conflict-related incidents across its reporting area, including 88 involving vessels in the Strait of Hormuz through October 28.

Is traffic recovering?

Marginally, yes — and from a very low base. UKMTO logged 122 outbound and 155 inbound transits in its latest seven-day reporting period, up from 114 outbound and 127 inbound the week before. Combined traffic nonetheless remains roughly 70% below pre-conflict levels. Around 80% of transits reported by U.S. Naval Cooperation and Guidance for Shipping involve energy carriers, meaning the exposure is concentrated squarely on tankers and the insurance markets that price them.

For shipowners and charterers, the October 29 attack adds a hull-level risk that patrols built around missiles, drones and moored naval mines were not designed to catch. Anchorage time — already a cost multiplier in a corridor where waiting vessels cluster near Fujairah and Khasab — now carries a distinct explosive threat. War-risk underwriters will read Kelly's below-the-waterline scenario as a potential total-loss event, not a fire-drill one.

Until operators can verify how the small boat closed with the LOUISE 1 unnoticed, the working assumption for any Hormuz transit must be that hull contact is possible in daylight, in traffic, on the designated safe route.