Image by Flickr user dglassme Not the dog in question, but you get the idea.
Update at the bottom.
The story goes like this, while dad slept two girls snuck outside and one got too deep in a West Ashley pond and would have drowned had the family dog not kept her above water.
Multiple reports abound but Live 5 News has the better report complemented with some raw video from the scene; get it here.
Update August 4: The Post and Courier has a later report which has a few more details; read it here.