Most civilians are completely unaware of how our Intelligence at sea works, like the Aegis surveillance systems on our destroyers, are not only decrypting and analyzing all communications from target vessels, but also triangulation to their sources and recipients, so they know who they are talking to, what they are talking about, and where everyone in the conversation is located. Not to mention the AVCAD (Aerosol Vapor Chemical Agent Detector) and CVCAD (Compact Vapor Chemical Agent Detector), which uses spectrometry to analyze chemical signatures and hydrocarbon data to identify and track every material on an enemy craft from up to 28,000 feet, in say a P-8A Poseidon aircraft Which is relaying all this info into a Navy network, shared by surface vessels and aircraft alike. Working together they have a very good idea of not only a targets cargo, but it's intentions long before our Navy vessels are even seen.