I have used cable as the others have, stretched across the creek, then I attach cattle panels that are free to swing with the current. Occasionally you have to remove sticks or washed out debris if it floods. Cut to fit the lengths. If you need it to ride on the water, some 4" PVC pipe capped off usually gives a enough bouncy. I have done this on several creeks from 10' across to over 40' and never had a cow/calf get out, or my horses for that matter.
I suppose it will also depend on what the creek is like?? is it large like the Mississippi , or 10' across???????