Roughly one-quarter of the non-Iranian large oil tankers trapped inside the Persian Gulf at the outbreak of the Iran war have managed to slip out in a slow, stealthy trickle. Twenty-nine of the 109 bigger vessels, those capable of hauling 700,000 barrels or more, which were stranded when the Strait of Hormuz was effectively shuttered after the conflict erupted on Feb. 28 have now crossed the chokepoint, shipping data compiled by Bloomberg show.