Of course we know there have been attempts to use true submersibles to transport cocaine, but this is the first I’ve heard of an effort to find them at sea. From http://defensetech.org/:

“Calling them “third-generation” Narco-subs, Adm. James Stavridis, supreme NATO commander said during a speech this week in Arlington, Va., that the U.S. and its allies in Latin America are using P-3s to hunt these actual submarines which have communications suites that rival some modern military subs.”

The article goes on to raise a good question, “All this begs the question, even if you can find a submarine from the sky, how do you know 100 percent who it belongs without getting it to surface? How do you get the vessel to surface for inspection during peacetime without serious kinetic action? Do authorities simply track the vessel and wait for it to arrive at its destination before moving into arrest the smugglers?”