Here's a shot (same trip, but I took it) of yet another pool in Slickhorn (from a March post).
Essence of river revealedThe San Juan is very strange. For one thing, it sometimes smells like an oil refinery: the stuff seeps from the cliffs into the water, which as a result not only stinks but is actually greasy.
For another, a phenomenon known as "sand waves" occurs on the San Juan. Here's a description of the natural oddity: "The waves, uncommon on most rivers, form because of the high silt load and the river’s steep gradient. Sand ripples form on the bottom of the river and waves build in response."
Something like that. Utah.com says, "Sand waves can form huge rippling waves up to eight feet high! They give a fun and certainly exciting ride." (How oddly phrased.)
Third, the San Juan forms part of the northern boundary of the Navajo Nation (another of those sites that won't let you link, God knows why; it's totally boring: www.navajo.org). Anyway, the left bank is all Navajo land and requires a separate (but cheap!) permit.
Update: Here's a San Juan River photography workshop. No idea if it's any good, but the site has some beautiful large-format photos.
Update II: A 1990 NYT article on the San Juan.
Update III: By "large-format" I mean the photos were taken with a large-format camera, not that they're huge files. They're not.