It appears to contain a central passageway and multiple chambers excavated from rock.
There is a large neolithic burial complex nearby called The Tomb of the Eagles where over 300 bodies were found.
“Potentially these skeletons could tell us so much about Neolithic people,” said Orkney Islands Council archaeologist Julie Gibson.
“Not only in relation to their deaths, but their lives.”
One end of the tomb was accidentally removed as it was discovered and as a result, the burial site has now been flooded.