How does this really work--they do not fall over the edge?

http://www.snopes.com/photos/natural/devilspool.aspHow does this really work--they do not fall over the edge?
A natural rock ledge reduces the current and stops swimmers from being swept over the edge. The pool is only safe to use at times of the year when water levels are comparatively low. At other times when more water flows down the river, the ledge does not offer enough protection for swimmers and the pool is inaccessible.How does this really work--they do not fall over the edge?
Apparently it has a natural barrier around it like a wall making it into a small pool on the edge of the falls. I'm not very good with heights and I'm not sure I'd go and swim in this thing.. Especially in th wet season. Look at the link below and it may show a bit more about it.
Well, it looks like there is a lip of rock that only allows an inch or two of water over. The current isn't strong anyway - it cant carry a human over.








ps - you couldn't pay me enough to get that close a cliff, haha. Regardless of whether or not it's likely I'll fall off.
The formation looks much like the edge of a poll. The edge of the rocks appears to form a lip with just a small amount of water flowing over that portion of the water fall.
The water flow bounces off the wall edge,and the result is a back-flow eddy current,but only when the water elevation level is low.
There's not much water flowing over the waterfall at that spot, so not much current to push them over the edge. It only works late in the year when the river is low.
GOD'S AMAZING ISN'T HE!!!!
i dont know..but i wanna go