My husband, who holds a number of patents in offshore oil drilling equipment and who has spent many hours on off shore rigs installing machinery, made the same observation. He attributes this disaster to operator error, or to deliberate sabotage. He does say that most rig workers are pretty straight arrow, so sabotage is a long shot. But, if he were hiring a crew, he'd want a thorough background check on everyone boarding the ship.
You mean making sure the 11 “missing” were South Koreans instead of North Koreans?