This type of catastrophe happened just a few years back in Rockingham Co, VA. Whole family (I think it was 5 total) but the little girl died in the early morning around sunup in a cattle waste lagoon that wasn’t hardly 6 feet deep with sloped sides. Each entered after the previous trying to save them from a low oxygen/asphyxiant atmosphere from no breeze and cold air.
Confined spaces are NOTHING to screw around with. If you can’t hook someone who goes down in an enclosed area/depression with a tool without entering, you need to leave them or the rescuers will be recovering 2 or more bodies.
I’ve seen videos where even the trained responders have gotten themselves killed trying to short cut/speed up a confined space rescue.
I remember that. . .
http://www.washingtonpost.com/wp-dyn/content/article/2007/07/03/AR2007070302136.html