It turns out the water is only about 18 inches (45cm) deep. That's what the local advised. And the floor of the crossing is rocks/gravel, not mud, also as advised. These are fine conditions for making the crossing in our Nissan Xterra 4x4. If the water were 24" deep I'd be more concerned. At that point it could intrude into the passenger cabin or cause backflow problems with the exhaust if I weren't careful.
Why cross the river? To explore deeper into the canyon!

Afton Canyon is full of colorful walls. There are also caves and narrows to explore. We'll get to some of those after a few miles of driving. In the meantime, here's another explainer about the canyon: