This is completely false. Water does a pretty good job of preserving shipwrecks, even from thousands of years ago. We're still finding ancient Greek ships now

This is completely false. Water does a pretty good job of preserving shipwrecks, even from thousands of years ago. We're still finding ancient Greek ships now, preserved by the oxygen-free water in the depths. Many wrecks have been found in the Black Sea, not far from where this place is, and many more surely remain to be discovered.