On maps dating as far back as the 1700s, Isla Bermeja was shown off the Yucatan Peninsula’s coast, at a greater distance than any other island claimed by Mexico. The island was just what the country needed to extend its claim on offshore oil and stop the United States’ encroachment on Mexico’s interests in that department. There was just one problem: A 2009 National Autonomous University of Mexico study concluded the island doesn’t exist—at least not where it’s supposed to be. The search team, using underwater sensing devices and aerial reconnaissance assets, couldn’t find the island anywhere in the area in which maps indicated it should be.

The island is supposed to lie 55 nautical miles farther than Mexico’s 200-nautical-mile territorial limit. By claiming it, Mexico would extend its oil claims into the middle of the Gulf. Although the lost island wasn’t found, Elias Cardenas, the head of Mexico’s congressional Maritime Committee, planned to continue his country’s search for it, hoping it might turn up elsewhere. Perhaps the island had sunk or submerged, he said.

Mexican conspiracy theorists had their own ideas about what happened to Isla Bermeja. Maybe the US bombed it, or it could have been a victim of global warming or an earthquake. Cardenas is certain that bombing didn’t account for the mysterious island’s disappearance. “That would have been [ . . . ] very noticeable,” he said.

The elusive island was first reported missing in 1997, when a Navy fishing expedition was unable to find it. Until it disappeared, Isla Bermeja, which supposedly measured 80 square kilometers (31 mi²), had been the point from which Mexico’s 200 nautical-mile limit started. Currently, the Alacranes islands have determined the end of the country’s territorial limits. As a result, Mexico’s “economic zone” has been “sharply reduced.