Here is a way to keep your pet's water bowls nice and cool for hours in the shade, especially during the summer months. Freeze clean plastic bottles and place inside the water bowl. Stainless steel bowls seem to keep the water a bit cooler and longer than plastic.
It suggests that you place a clean plastic bottle that you have frozen, in the pets water bowl to keep it cool.
It does not say if you fill it with water or not.
