I don't know about the credibility of the source, but
this early report,
"To the attack itself, these reports continue, the North Korean “cargo vessel” Dai Hong Dan believed to be staffed by 17th Sniper Corps “suicide” troops left Cuba’s Empresa Terminales Mambisas de La Habana (Port of Havana) on April 18th whereupon it “severely deviated” from its intended course for Venezuela’s Puerto Cabello bringing it to within 209 kilometers (130 miles) of the Deepwater Horizon oil platform which was located 80 kilometers (50 miles) off the coast of the US State of Louisiana where it launched an SSC Sang-o Class Mini Submarine (Yugo class) estimated to have an operational range of 321 kilometers (200 miles)." And before you LOL at the concept of the term "Sniper Corps", yes that's an honorific unit designation amongst the dprk SOF forces.