Re:Dozens of oil tankers cluster off the coast of Texas due ...
by hydrogen18 on Friday November 13, 2015 @11:28AM
(#10560658)
Most likely the captain choosing to turn it off. If you look at Coast Guard & Pilot boats they'll usually leave it on as they leave the dock and make their way out. Then it's off. Not very effective at interdiction if you're broadcasting your location.
http://imgur.com/CRbS9nD
edit: It looks like the website either hides the locations of ships off the Somalia/Yemen coast, or the ships can choose to turn off their transponders there.