More than 400 oil tankers are stranded in the Persian Gulf as Iran’s threats to disrupt shipping through the Strait of Hormuz escalate, effectively closing the vital waterway to conventional maritime traffic. The standoff, which began in early March 2026, has sent ripples through global energy markets and exposed a hidden network of vessels operating outside international regulations – a “shadow fleet” increasingly relied upon to circumvent restrictions.
Iran has warned it will destroy any ships, including oil tankers, attempting passage through the strait, a narrow channel separating Iran from Oman and the United Arab Emirates, through which roughly 20% of the world’s oil passes, according to the Independent.
The crisis has prompted insurance companies to reassess coverage for vessels transiting the region, with some offering policies only on a case-by-case basis. The International Maritime Organization has advised crews they have the right to refuse sailing into the area, further exacerbating the logistical challenges.
While many law-abiding shipping companies have halted operations, a subset of vessels continues to navigate the strait. These ships, dubbed the “shadow fleet,” routinely operate outside the bounds of international maritime law, ignoring restrictions on trade, violating anti-pollution regulations, and engaging in illicit smuggling. Their existence highlights the fundamentally voluntary nature of the system governing the world’s oceans.
The foundation of maritime tracking relies on the International Convention for the Safety of Life at Sea (SOLAS), signed by 167 countries, which requires commercial vessels to broadcast their identity, position, speed, and heading via radio transponders. Yet, as Britannica notes, there is no mechanism to prevent crews from disabling these transponders or transmitting false data. When a vessel “goes dark,” it simply disappears from all tracking maps.
National jurisdiction is also a matter of preference, not law. Ships sail under the flag of a nation, theoretically responsible for their regulation and inspection. However, ship registration has develop into a commercial transaction, allowing vessel owners to register in countries with lax oversight, such as Cameroon, Palau, or Liberia, or even landlocked Mongolia, as detailed by Wikipedia. Vessels can even re-register under different flags to evade scrutiny.
Insurance represents the closest thing to an enforcement mechanism within the maritime system. Major insurers require adherence to safety standards, proper documentation, and compliance with international trade sanctions. However, a significant portion of the maritime industry operates outside this framework. Reports indicate that approximately two-thirds of ships carrying Russian oil – subject to U.S. And international sanctions – have “unknown” insurance providers, raising concerns about accountability in the event of spills or collisions.
Recent incidents underscore the challenges of enforcing maritime regulations. In December 2025, the United States seized a sanctioned tanker, the Skipper, flying the flag of Guyana, despite the country having no record of its registration, effectively rendering the vessel stateless. Another vessel, the Arcusat, altered its unique International Maritime Organization (IMO) identification number, akin to removing a vehicle identification number (VIN) from a car.
The shadow fleet operates by acquiring aging tankers, registering them through shell companies, obtaining flags of convenience, utilizing opaque insurance, and disabling transponders when approaching sensitive areas. They facilitate the transport of sanctioned goods, often through ship-to-ship transfers on the open ocean, to buyers who avoid scrutiny. According to maritime intelligence firm Windward, approximately 1,100 dark fleet vessels, representing 17% to 18% of all tankers carrying liquid cargo, are currently operating globally.
The emergence of the shadow fleet is not a sign of a broken system, but rather a consequence of its voluntary nature. For decades, compliance was the most cost-effective option. However, international sanctions have made compliance prohibitively expensive and politically risky for some, incentivizing the creation of parallel systems. Iran began developing such a system in 2018, following the reimposition of sanctions related to its nuclear program, and Russia expanded it significantly in 2022 after its invasion of Ukraine.
With the Strait of Hormuz effectively closed to legitimate maritime trade, the shadow fleet has become the primary means of transporting oil. This development raises questions about the future of maritime regulations and the willingness of nations to enforce them. Reports have surfaced of ships turning off their Automatic Identification Systems (AIS) to evade tracking, and companies like Greek firm Dynacom are reportedly continuing operations through the strait despite the risks.
