I was recently reading a book on the ocean and apparently sea water softens bones and they then break down quite quickly. An interesting thread, BTW.
I recall seeing an artefact in the museum at Portleven in Cornwall that consisted of an engine bearer. The bearer was associated with a Beaufighter wreck but was in keeping with having held a Merlin engine. Of course, the Mk IIF had Merlins as a contingency against shortages of the Bristol engine. Amazingly, no one seemed to know that IIFs had operated from Cornwall.