I wonder if it would be possible to get them to germinate. Old seeds have been successfully germinated in the past, but I suspect the underwater-thing might have made it impossible.
Can't find the article right now, but people have successfully drunk 2000 year old wine that was laying in amphorae at the bottom of the sea, preserved by a layer of olive oil which was placed on top to keep the wine from oxidizing. The Mediterranean is full of interesting stuff.