In early 2014 U.S. Navy submarine detection experts got a scare when a Russian Vishnya class AGI (Auxiliary General Intelligence, or electronic reconnaissance) ship was seen several times off the east coast of Florida, in the vicinity of naval air and submarine bases. The Vishnya spotted off Florida was accompanied by a sea going tug. Both ships used Cuban ports for resupply. The two ships apparently first showed up in Cuba in February. What scared the submarine detection crowd was the recent realization that computers had become cheap and powerful enough to make it possible to detect submarines via the faint signs (like disturbance of the surface waters above them) that they leave. It has been known for decades that these telltale signs existed and that with sufficient computing power and sensitive enough sensors you could use this method to track submarines in real time. In other words, it no longer mattered how quiet a sub was, just whether it was there or not and moving. U.S. Navy experts had been doing the math and realized that the time was rapidly approaching, if not already here, when the sensors were sensitive enough and the computers fast enough to unmask all current subs.
“All current subs” would of course include our 14 Ohio-class nuclear missile boats, carrying over half the deployed warheads of our nuclear deterrent.