For two months, the Malta-flagged oil tanker Alkimos has been quietly floating off the Gulf Coast of Texas, undisturbed by the high-stakes legal fight playing out in a federal courtroom as a result of American sanctions on Venezuela. The commercial dispute, which hasn’t been previously reported, has all the drama of a pirate movie: a precious cargo, clandestine sea maneuvers and accusations of a high seas heist. It pits Evangelos Marinakis, one of Greece’s most powerful businessmen and owner of its most successful soccer club, Olympiakos, against a fellow shipping magnate from Venezuela, Wilmer Ruperti, who has a long history of helping the country’s socialist leaders.