Crossing something like this in flip-flops would be no bother...
But something like this might be rather more "interesting"...
Falling over in the fast rocky rivers may be preceeded by seeing one of your flip flops disappearing downstrem after the current has removed it from your foot...
I'll often ford stuff in Teva Terra Fis, but I'll have them on anyway. I wouldn't cart something that heavy (or buy something that costly) just for river crossing. But whatever I used I'd want it to be able to be attached reasonably firmly to my feet if I'm doing something like the second photo above. The job of keeping a flip flop on in that sort of thing also needs to consider your feet are numb after the first few seconds (a lot of that's melt) and the bottom is very uneven and slippery.
Pete.
Edited: 09/09/2011 at 11:44