Russia's submarine fleet, asleep after two decades without a mission or money to patrol the sea, is starting to show life again. This week came reports that Russian attack submarines are "prowling" the coastlines of Scotland, Scandinavia and the Mediterranean Sea in numbers not seen in years.
CNN: How big a threat is Russia’s submarine program?
Russian naval flags are seen on the Zaporizhzhia' former Ukrainian submarine moored in the bay of the Crimean port of Sevastopol on April 17, 2014.
