Verified videos and satellite images show oil from the 3 August strike on the Minoan Pioneer washing onto Qeshm Island, with analysts tracing the spill from Omani waters across the Strait of Hormuz.
More than 300 sq km of slick was visible by 10 August, and SkyTruth estimated the spill at well over 100,000 gallons after the Liberia-flagged bulk carrier was hit by a projectile and leaked fuel.
Qeshm's mangroves, coral habitats, fishing grounds and Hawksbill turtle nesting sites are at risk, with experts warning oil reaching the seabed could cause damage that persists for years.
Iran said the pollution came from a foreign bulk ship, while a local environmental official said the spill was almost completely cleaned up, a claim that BBC Verify could not independently confirm.
The spill adds to mounting environmental fallout from attacks around Hormuz, where Kpler has logged 67 vessel strikes since late February amid widening US-Israel-Iran conflict.