I all,

I have a polished river stone floor in my shower, with black grout, problem is, it has a white haze from the water. I would like to know how to bring back the deep black that was originally the grout color. Is there a superior cleaning product? Have any of you had luck cleaning grout in the shower area. Thanks for any advice!

Try CLR which is in the laundry aisle at most grocery stores and hardware store.

Your problem is minerals leaching out of the grout, this is a coman problem with cement.
I use different grouting tricks to avoid this but there are different (efflorescence) removers out there look at the hardwhere store