There Was Enough Light To Conduct A Thorough Excavation
Much of the sand surrounding the wreckage was infertile, meaning that it was light enough to reflect the light of the sun from the surface of the water. This was especially helpful during excavation.
It was a good thing that the archaeologists had all this light too, since they were in for a massive discovery that included more than 30,000 artifacts. It would take many years for them to uncover everything.