I think an ejectable and floatable locator should be mandatory. Located in the fin, possibly, ejected either by hydraulic or air pressure stored in an accumulator, (one way valve, in the event of system failure), and of sufficient force to clear the tail plane if the ejection occurs with the aircraft inverted. Triggers could be shock above a certain pre determined value and on immediate contact with water.
Awaiting to be shot down by the engineering fraternity!
