There's a water table that rises and falls with the Nile level. That symbolic 'tomb of Osiris' discovered and excavated about ten years ago has to be keep pumped out, for example. And one of the supposed Old Kingdom temples usually has water standing.
Learnt something new. I thought the Osireion WAS the original Tomb of Osiris since it appears to me of the megalithic age predating the Predynastic and/or Protodynastic to the more "modern" Dynastic age of Egypt.