ON THE SAN JOAQUIN RIVER (CNN) -

Halfway through my three-week, 417-mile journey down the "most endangered" river in America, the water began flowing backward and the mud started talking.

It spoke in baritone gurgles, like Barry White trapped in a bong.

You know what this is, John?

No, Barry White mud.

This is QUICKSAND.

*&#%.

Despite my overactive imagination, this ridiculous situation was real: The quicksand -- I didn't actually _believe_ in quicksand until that afternoon -- bubbled and spat as it slurped me down and held on tight.

It had me at the knees.

As anyone who's seen "Indiana Jones" or "Princess Bride" can attest, you need a sidekick to get unstuck from quicksand. No sidekick here. I was alone on the San Joaquin River in California's remote Central Valley -- the forgotten part of the Golden State, where no one thinks of taking a vacation.

I looked to the left to see this Frankenriver flowing backward -- toward the Sierra Nevada, where I'd started this "Mad Max" journey 12 days before.

I had no idea what was going on.

Or how the hell I was getting out.

The San Joaquin, the second-longest river in California, used to support ferry traffic.

Now there's not enough water for a kayak and me.

That's why I'd started walking in the first place, dragging my boat by a rope.

The quicksand was just one of the semi-apocalyptic challenges I'd face on my trip down the San Joaquin, from its headwaters in the Sierras, near Yosemite, to my hoped-for destination, beneath the Golden Gate Bridge in San Francisco.

Here's the route:

The San Joaquin is a river that would flip my boat, steal my camera, throw me into trees, take my food, tweak my muscles, acquaint me with heat exhaustion, scare the s--- out of me, trap me in the mud and leave me hiking for three days across a desert.

It even fertilized me in the middle of the night.

And that's just the me-complaining part.

Far worse, it also deforms birds (or did, in the 1980s), taints taps, steals jobs, causes the ground to sink irreversibly, kills fish, destroys wetlands -- and harbors shady people with semi-automatic weapons.

Still, it's somehow also a river that supports a valley that grows 40% of the nation's fruits and some vegetables as well as more than 80% of the world's almonds. It's a hugely important river, but one that's been engineered almost to death.

Thanks to the Clean Water Act, rivers don't catch fire from industrial pollution like they used to. Here's what Ohio's Cuyahoga River looked like in 1952.

Now we're in the era of dead rivers -- a time when they've been so dammed, diverted and overused that many of them simply cease to flow.

Last year, CNN readers voted for me to do a story on the "most endangered" river in the country as part of my Change the List project. Many rivers could vie for that title. Earlier this year, the Colorado River flowed to the sea for the first time in decades -- and that took an international agreement. The Rio Grande, which forms the U.S.-Mexico border, often doesn't make it to the ocean, either. And the Mighty Mississippi is so polluted by farms that it feeds a Connecticut-sized "dead zone" in the Gulf. The advocacy group American Rivers, however, chose the San Joaquin as the "most endangered" river in 2014 because it's at a turning point. Depending on what happens soon, it could become a river reborn, or a drainage ditch.