Working in fast moving water

[freediverND]

Might be a good idea to plan the very, very simple too.  Maybe you'll get into rivers that have a "not so bad" current, then a simple spike that can be added to the camera could work as an anchor and mono-pod.. if the substrates are such that you can push it in to the bottom.
I thought hookah earlier too..  I'd like to get one of those for the grandkids (and myself), but then, like the tender line, you'll have to deal with that getting in the way of some shots you want to take.  It would sure work good for collecting lures, but in a fast current would almost have to be on the shore, the ones I've seen are not at all streamlined, the drag on it would be tremendous if it was anchored.

you'll figure something out.  good luck.