Transit through the Strait of Hormuz remains active but constrained, with relatively balanced inbound and outbound movement, and continued reliance on diverse flag registries, according to Windward analysis.
As of 15 April, 15 vessels were observed in mid- or post-transit, comprising eight inbound and seven outbound crossings. Inbound traffic included five tankers flagged to Malta, Angola, Malawi, and the Netherlands Caribbean, along with one Panama-flagged bulk carrier and two cargo vessels flagged to India and Comoros.
Outbound traffic included one Bahamas-flagged tanker, one Malta-flagged bulk carrier, and five cargo vessels, with flags of India, Comoros, and Iran represented. This pattern indicates continued operational activity, though routing behavior and participation have not yet returned to normal levels.
U.S. enforcement and vessel behavior
U.S. Central Command has confirmed that at least eight Iran-linked oil tankers have been intercepted since the start of the blockade. In each case, vessels were contacted via radio and instructed to reverse course, with full compliance and no need for boarding actions.
The blockade is being enforced against vessels of all nationalities entering or departing Iranian ports, with U.S. forces maintaining maritime superiority and actively monitoring compliance. More than 15 warships and additional personnel have been deployed to support enforcement.
This confirms that the blockade is operational rather than decelerative, with early-stage enforcement already altering vessel behavior without escalation.
Iranian exports continue at scale
Iranian oil exports remain structurally active, despite the enforcement environment.
As of 15 April, approximately 153.7 million barrels of Iranian oil are on the water, with 84.9% destined for China. Average daily export volumes from Kharg Island between February and April remain elevated at approximately 2.04 million barrels per day.
Satellite and AIS analysis confirms at least two VLCC departures from Kharg Island immediately surrounding the start of the blockade. Two Iranian-flagged VLCCs, each loaded with approximately 2.01 million barrels, are bound for Dongjiakou, China.
Vessels with Iranian oil on water, April 15, 2026. Source: Windward Maritime AI™ Platform.
One VLCC remains at the eastern terminal, which continues to display deceptive behavior by reporting a false destination and spoofing its location approximately 44.5 nautical miles west of Kharg Island. These patterns confirm that Iranian export flows remain active, supported by both physical loading and deceptive shipping practices.
Gulf activity remains high under constraint
The broader Gulf remains active, but under constrained and monitored conditions. As of April 15, total vessel presence stood at 823, an increase of 13 vessels from the previous day. Furthermore, dark activity events declined 3% to 148.
Flag distribution continues to be dominated by Panama (134 vessels), followed by the Marshall Islands (75), Iran (74), Comoros (73), and Liberia (64). The fleet includes 150 bulk carriers, 137 product tankers, 75 crude tankers, and 62 container vessels.
China-linked presence has increased to 101 vessels, including 68 cargo vessels and 33 tankers, reinforcing continued demand-side support for Iranian exports.