Emergency locator beacon (ELB)
I'm truly amazed that no technology exists to eject an emergency locator beacon (E.L.B.) in the event of ditching on the high seas the device could be ejected using a similar device to a vehicle airbag,aft of the pressure bulkhead of course and the device could be on the surface, within seconds if not minutes,and preferably with solar cells to keep the transmitter active as long as possible,finally if the E.L.B had a tether to the structure of the aeroplane
once (the beacon) had surfaced the ditched aeroplane could be located fairly quickly under the waves. I know about the underwater ping type beacon,
but if there is a transmitter atop the the waves, then everybody should know about it's location within a short space of time.