The fish flopped violently about on the wooden floor of the boat, its razor-sharp teeth chomping, the sound echoing in the silent, waning afternoon.

The river was calm and there was no wind, the trees still, the sun getting noticeably lower by the minute. On either side of the water was thick, nearly-impenetrable rainforest, cutting off the horizon in two directions – the clear path of the river was an exception, not the rule.

I picked my feet up off the floor and held them tight to my chest. Most of us were wearing sandals, and an exposed toe can quickly disappear in this neck of the woods. Or so I had learned earlier. In fact, I had been introduced to the perils of piranha fishing before I ever held a rod.

I’m aboard Amazon Nature Tour’s Tucano, about a three day sail up the Rio Negro from Manaus, Brazil. This morning, when the captain came down to breakfast, he was wearing a large bandage over his thumb. He hesitated when I asked him what had happened. It looked like he didn’t want to tell anyone. But we were days from any sort of help, and when you’re that far out in the wilderness, the captain’s health becomes everyone’s priority. I turned to the guide.

“What happened to him?” I half demanded, half asked.

The guide drank his coffee and smiled. He made a chomping motion with his thumb and fingers.

“Piranha,” he said, smiling.

The word might as well have been accompanied by the banging of a giant gong. Piranha. It’s the most feared creature in the Amazon, at least in the public’s imagination. An anaconda might be a mythical killer, but rarely do they interfere with humans. A piranha, by comparison, is responsible for 100s of reported attacks per year – and probably thousands more unreported.

Our captain, for example. Last night he went fishing off the back of the boat. He caught a piranha and got bit “trying to take the little f’er” off the hook, the guide said. I took great joy in this explanation, and I laughed with the guide about it. He thought the whole thing was pretty funny.

“Everyone has a story like that,” he said.

I was laughing, but when the captain peeled back the bandage and showed us the chunk that had been taken out of his thumb, I was pretty terrified. We were, after all, scheduled to go piranha fishing later.

“Is this a joke?” I asked, “Something to scare us?”

The guide straightened up. “No, it’s not,” he said.

I immediately told everyone else on the boat what had happened to the captain – I’m kind of a gossip – and they all had a different reaction. Some were motivated, thinking the fishing experience would be “epic.” Some were worried. “And we’re going to fish for them?”

I was somewhere in between. Cautiously optimistic, you might say. I had heard the little buggers are tasty… but maybe they were thinking the same about me?

Later that afternoon we boarded a small dingy and rode out to the shallow banks of the river.

Read the rest of this story on Forbes.