Here's Craig crossing the Fords of A'an on the CL last September
And Ian Fitz a few minutes later.
I think we all used the bike forward and downstream of ourselves, front axle level with body. I don't know about Craig and Ian but I used the bike as both a support and as a means of pulling me forwards in a weird sort of ferry glide: if you turned the front wheel slightly away from you it would pull the bike forward.
I crossed the first part of the river at slack water leading to the top of the "island" which was very roughly at the right edge of the first photo then crossed the second part in the big "smooth" area up and to Craig's right. When Ian arrived we directed him this way. White water indicates that just upstream there's irregularities (boulders) in the river bed, that doesn't mean the bed is smooth but it's not as rough as at the top edge of the white water, also the bed gets scoured in these locations so can be deeper. What's also obvious from the shots is that you can't see the river bed in the white water areas.
For less dramatic conditions: find the widest part of the river as it will be shallowest. Contrary to the above about white water, stony areas of river bed are often the easiest to cross and you often find just a short channel blocking your way.
