London CNN — Russian oil is still finding its way to buyers around the world. But even those who spend their days tracking its movement across oceans struggle to work out exactly who is ferrying it. As Western sanctions against Russia have escalated over its invasion of Ukraine, more ships have joined an existing fleet of mysterious tankers, ready to facilitate Russia’s oil exports. Industry insiders estimate the size of that “shadow” fleet at roughly 600 vessels, or about 10% of the global number of large tankers. And numbers continue to climb. Who owns and operates many of these ships...