Maybe a dumb question as I haven't seen it asked by anyone else but is it possible to make FDRs floatable? I know they're pretty dense but there has got to be a way to make them buoyant, eg by using a polyurethane foam casing or some other ultra low density material.
It's such a shame that they're otherwise pretty indestructable but that's of absolutely no use when they're functioning perfectly where no one can find them, under 20,000 feet of water.