When I showed up to go white-water rafting in Uganda, Josh, the Canadian rafting guide who stood barefoot in board shorts and looked like a hardier, hairier version of Brad Pitt, greeted me with a simple question: Wild or mild?

My advice, if you’re ever going to do this, is to choose wisely. Because the next thing I knew, I was upside down in an infuriated patch of the Nile River, a ceiling of white water above me, all those tranquil birds and flowers along the banks a violently disappeared memory and Josh screaming, “Dude! Watch out for the rocks!”

And that was just Round 1. Our rubber raft flipped countless times. We went flying off waterfalls. We got twisted around rocks. The whole experience was like riding a bouncy castle through a tsunami. In some places, the water seemed to defy the laws of physics, with giant, green frothy waves crashing into one another at impossible angles. The scariest rapid was aptly called the Bad Place. It, indeed, was pretty bad.

But the Nile, that historic source of life gushing 4,000 miles across Africa to the Mediterranean Sea, was exceedingly beautiful — all we could see along the banks were miles and miles of pristine woodland, no garbage, no development, no fences, just cormorants and monkeys and the occasional crocodile lounging in the sun. The water was warm and clean, perfect for getting dunked into. The guides, who were a mix of expats and Ugandans, were funny, skilled and safe.

When my colleague Vanessa and I began our rafting trip, we landed at 9 p.m. at Entebbe airport. We had to get to Jinja, the hub of Uganda’s booming rafting business. We drove two and a half hours through the countryside, through inky blackness. And guess what? We were fine. We spent the night at the Jinja Nile Resort, a serene hotel perched on bluffs overlooking the Nile, and the next morning, the fun began.

“Listen up, folks!” boomed Josh, the rafting guide, whose blond locks dangled from under a beat-up construction-site hardhat. “No shoes, no flip-flops, no necklaces, no nothing. If you don’t want to lose it, don’t bring it. If we flip over — and you will flip over — hold on to the raft. Now, who wants to go wild?”

Without thinking, everybody in our 60-person group, who were mostly 20-something students and backpackers from England and the United States, cheered out “wild!” — the more aggressive course. If you want to go mild, which, by the end of the trip, many frazzled rafters had switched to, you float down the same stretch of river, just with your guide steering clear, or trying to, of the most intense rapids. Rapids are rated by numbers, 1 through 6. When I asked Josh to break it down for me, he said: “One is basically flat water, like a swimming pool.” Two and 3 can be bouncy, 4 and 5 pretty tough. And 6? “Death likely.”

To make sure that didn’t happen, Josh put us through the paces, teaching us how to stroke, how to hold on and how to get back in the raft if we got tossed out, which actually took a lot of strength and always ended in a thoroughly undignified wiggle.

Our first test was Big Brother. I never got a good answer as to who had named Uganda’s rapids, but the names were impressive, like Hair of the Dog, Vengeance, 50-50 and, of course, my favorite, the Bad Place. Most were Class 3 and 4. Big Brother was essentially a waterfall, and we pulled hard on our paddles and then let the falls suck us in. The awesome power of the Nile surged beneath my feet. The roar was deafening. I remember right before we hit the falls, looking up and seeing some paper-white egrets cruising in the sky, totally oblivious to the terror we were about to experience. “Everybody get down!” Josh yelled.

The raft smacked into a torrent of white water, and in milliseconds, our bouncy castle was swamped. The river was actually swirling inside the raft, trying to yank us out. I clenched the safety rope along the edge with all my strength. My heart was pounding. My grip was slipping. This lasted for all of about three seconds. And then, poof! It was over, and we were floating through flat water again.

Aw, that wasn’t so bad, I was thinking. I even slapped someone a high five. But then I looked down at my left hand. Um, wait a sec. Where’s my wedding ring? The one my grandfather made and wore at his wedding? The one thing my wife would kill me for losing? Gone. At the bottom of the Nile. Gulped down by Big Brother. A cherished family heirloom reduced to 18-carat fish food. Crestfallen, I asked Josh if such a tragedy had ever struck a rafter before. “Happens all the time,” he said. “Did I forget to mention that at the beginning?”

Eventually, I got over my loss and was able, once again, to enjoy the white water and the scenery. Most of the river is actually placid, sometimes a mile wide and calm as a Wisconsin lake. I could see thatched huts in the distance with smoke lifting off their pointy roofs. And walls of leafy green banana trees. And huge monitor lizards slithering across rocks. When we got hot, we just jumped in the Nile and floated on our backs, searching the sky for that perfect cloud, toes pointed north, toward Egypt.

The guides were careful about the crocs — which, yes, do bite, and in the few known crocodile hang-out spots, we weren’t allowed in the water. Every once in a while we’d pass fishermen paddling along in log canoes. Some didn’t bother with clothes. Lily, an M.I.T. grad on my boat who recently lost her finance job, was inspired. She suddenly jumped up, peeled off her bikini, snapped her lifejacket back on and resumed paddling. ”Uh, excuse me,” asked one of the young Brits on the raft, with a look of genuine shock on her face. “But why exactly are you rafting naked?” “The question is,” Lily shot back, “why aren’t you?”

I didn’t have time to settle this before we hit 50-50, one of the nastier rapids, where two forks of the river collide and drop like a precarious set of stairs. The Bad Place, a thundering, angry vortex that looked as though it was powered by a jet engine just under the surface, was right next door, but the water was too low and therefore too dangerous for us to run it. We learned that 50-50 was scary enough. “On this one, if you fall out,” Josh screamed, cupping his hands over the rising din, “don’t even bother try holding on!”

We plunged. The curl of a wave lifted our boat straight out of the water and flipped us upside down like an egg in a skillet. But instead of immediately popping back up, a bunch of us got trapped under the raft, with the rapids pushing it down on top of us. It was terrifying, because there was no way out. I kicked. I thrashed. I felt as though I swallowed a gallon of river water. I started thinking of that scene at the end of “Titanic” in which Leonardo DiCaprio drowns. And then, pop, the raft shot away, and I broke through a fury of white water and feverishly gulped for air. That’s when I noticed everything was a little fuzzy, which leads me to casualty No. 2, my right contact lens. Gone. I spent the rest of the trip squinting through one eye.

That night we licked our wounds and drank cold beer at a campsite on a bluff above the river. The guides made us dinner — rice, salad and a chicken stew with peanut sauce, all served family-style out of big, dented pots. I polished off several plates and then slept like a baby in my tent.

It was the perfect way to end the trip. We climbed back on the bus, exhausted, sunburned, shoulders sore and feet raw. The engine sputtered to a start. I looked around at the other contented faces of the group and felt that we all had been through something together. I squinted through my one good eye and tried to forget about my newly vacant ring finger. I watched the Nile slide away behind us, smooth, green and inviting as ever.