Leopard Gecko burys water dish

Question
This 8 y/o Leopard has gone from occasionally digging to fill its water dish with substrait, to filling its water dish every time I fill it with water! Almost as soon as I fill it. Why?

Answer
 The water dish is usually a lizard's place for a bath, maybe a sip, probably a poop, and some leos have laid eggs in it.  He may be just trying to make his environment to his liking, like he'd prefer a moister substrate, or he just needs to dig there.  I would try to moisten the substrate a bit and then give him fresh water and see if he does it again.