Determining the country with the most submarines in its military arsenal is a bit tricky. Nations often keep their military statistics classified, so exact numbers aren't always available.

Satellite imagery spotted a Chinese submarine with its nuclear ballistic missile hatches open while pier-side at a naval base with underground facilities facing the contested South China Sea.

At the Wisconsin Maritime Museum in Manitowoc, you can descend a steep staircase into the USS Cobia, a US Navy submarine that sank 13 ships and earned four battle stars in World War II.

And did he know about the Soviet-era submarine? Agents showed him photographs of one in a navy yard in St. Petersburg, Florida, with someone resembling Fainberg posed awkwardly next it.