SPY satellites. You have no idea what they are monitoring because that is classified. I provide links and all you provide is ignorant opinion. Have you heard of RIMPAC? I know why Simpson was able to "sink" the Independence. Trump needs to be careful about what he is doing. http://www.g2mil.com/thompson.htm
“U.S. Navy exercises with diesel submarines since the mid-1990s have often proved humbling.” – John Benedict, National Security Analysis Dept., Johns Hopkins University Applied Physics Laboratory, 2005. 
To be more specific, during RIMPAC 1996, the Chilean submarine Simpson was responsible for sinking the carrier USS Independence (this event was chronicled in the 1997 Discovery Channel TV documentary “Fleet Command.”) http://nationalinterest.org/blog/the-buzz/swedens-super-stealth-submarines-are-so-lethal-they-sank-us-18383 http://nationalinterest.org/blog/the-buzz/2015-30-year-old-french-nuclear-submarine-sank-us-aircraft-18912 Carrier groups are acoustically blind.