Count, If you're doing DD. You might want to add this to your check list.
If I am not mistaken. Jay stated that the 65,000 emeralds he recovered were just lying on top of the ocean floor. Jay also stated that the ocean bottom was mud at the emerald location.
Check the internet for the specific gravity of emeralds and the specific gravity of mud. I think you will find that scientifically the emeralds should have been under the mud and not on top of it.