Iran’s Shadow Fleet Kept Hormuz Flowing During U.S. Blockade

*TL;DR: 202 vessels crossed the Strait of Hormuz from March 1‑April 15, 38.5% tied to Iran, and 25 ships slipped through the U.S. blockade.

Context The Strait of Hormuz carries about one‑fifth of global oil. After a temporary ceasefire on April 8, the United States imposed a full naval blockade on Iranian ports on April 13, aiming to halt all traffic.

Key Facts Al Jazeera’s Digital Investigative Unit logged 202 voyages by 185 vessels during the 45‑day window. Of those trips, 77 vessels (38.5%) were directly or indirectly linked to Iran, and 61 ships appeared on international sanctions lists.

The investigation split the period into three phases. In the “Open War” phase (March 1‑April 6), 126 ships crossed, including 46 Iranian‑linked vessels. The “Truce” (April 7‑13) saw 49 crossings, with over 40% tied to Iran; the sanctioned Iranian‑flagged tanker Roshak exited the Gulf.

During the “U.S. Blockade” (April 13‑15), 25 ships still traversed the strait. Smaller Iranian cargo ship 13448 evaded detection by lacking an IMO number, sailing from Al Hamriya to Karachi. The Panama‑flagged Manali also breached the cordon on April 14 and again on April 17 toward Mumbai.

Vessels routinely disabled or jammed AIS signals—automatic trackers that broadcast a ship’s identity—to hide routes. Ships such as Flora, Genoa and Skywave deliberately turned off their transponders.

Operators masked ownership with false flags from landlocked registries like Botswana and San Marino, and shell companies spread across Iran, China, Greece and the UAE. Sixteen ships used such fake flags; ownership of nearly one‑fifth of the fleet remains unknown.

Energy carriers dominated traffic: 68 ships (36.2%) carried crude, refined products or gas, ten of them linked to Iran. Non‑oil bulk cargo also persisted.

What It Means The data shows that the blockade failed to stop commercial flow, thanks to a covert “shadow fleet” that exploits legal loopholes, signal jamming and opaque ownership structures. The ability to move oil and goods under fire suggests Iran can sustain trade despite direct military pressure.

Looking Ahead Watch for diplomatic moves to tighten flag‑registration rules and for any escalation in U.S. naval enforcement that could further test the shadow fleet’s resilience.