Outstanding! It just so happens I have a large block of natural clay that I can mix with the dirt.When I was young in Indiana we boys kept painted turtles. To make a pond for them we dug a hole and then went down to the creek and hauled back as much clay as we could. We covered the dirt in about 2-3" of clay. The thing held water like a charm.
Top soil makes mud - but clay has a greasy content that holds water. We only had to run the hose in there once a week to maintain our " pond".
No luck digging the mud pit last night, we had a big storm come through with torrential rain, high winds and a lot of large hail. It did a bit of damage to some of the plants and gardens on the deck and knocked down pretty much every plant in his playpen. It looked like a tiny tornado went through it.
I think everything will survive, but it was quite a mess!