The sketchy-thing, actually is one of the things I like most about this forum.
Yes, I'm a bit of a river person, canoed and/or kayaked most of my life now and the river certainly is deceiving, including flow/current. Not necessarily so, what's readily seen to the naked eye but that's a big part of the draw in its magnificence. You're right, this is very much also good reason to use caution, it's quite on the side of dangerous as it is beautiful. Like you're saying, there is all this to think of and then deeper yet is the issue of the soil, for example. It may appear solid where you see bottom but that's often, in actuality, a formiddable layer of muck and silt three or four feet thick where I come from. Very key point if you tip either a canoe or kayak.
We have a lot of ecological law of the land here, not mentioning building code where I'm at, many river-specific enforced guidelines protecting both, I've wondered in the past why these are used so much as a template in other, disaster-plagued areas...
Yeah, this 'river' flows faar beneath the Amazon, it was that and the fact it ran parallel that piqued my interest, so cool, beyond words, I was surprised it didn't get more coverage.