Caught some interesting coverage on this by a pretty reputable aviation writer (styled by the media as an 'Aviation Archaeologist') who ran through the three sites identified.
He stressed the fact that most of these areas have become wet zones, aside from rising water level through natural causes, the construction of dams, diversions and intensified farming has made the entire country 'wetter'.
After 68 years he really doubts that anything as fragile as a Spitfire would do very well at all, given the brackish water, heat, subsidence and who knows what chemical pollution from farming has done.
We all hope that something might emerge but the chances are not good.