waterlogged shed base

Hi all, I have dug out a space for a shed a few months ago, but with all the rain it has become waterlogged!!! I am now not sure as to what or where to start or go from here!!! I am aware I need to level it out but I am uncertain as to how as the mud is more like clay, all lumpy and stuck together and very hard to move around..... Is there anything that will dry the mud out i.e sand / ballast??
Thanks Guys

Gravity. Either don't put the shed in a hole, or have the shed 'hole' drained to a lower part of the garden. Even then you will have water constantly passing through the hole so I would suggest you fix it 'above ground'.