CNN Anderson Cooper 360 March 11, 2014 05:22:00
Transponders and transmitters lasts for about 30 days. but there have been evidence it has lasted considerably longer. if it is underwater it will be more difficult to hear the ping or receive that information which is why more boats are being brought in with more sophisticated sonar equipment that will be able to better read and understand and understand if it is pinging. that assumes it is in one piece and working normally. but the location of these transmitters is such and the way they are built is so robust, they are built specifically with the thought of the -- of an incident and accident...
Source: archive.org