Diving into the Amazon

It's dawn, and my sister and I are huddled at the back of a long canoe gliding along the Rio Negro, the Amazon's 'Black River'. The glassy water lives up to its namesake, with barely half a meter of visibility despite the growing intensity of the early morning sun. We're en route to swim with the rare Amazon river dolphin. With us is our mum, a witty Danish family, and our guide, a stout Pakistani fellow named Mike.
We disembark the canoe at a small river station where minutes later, donned in our swimmers and dashing fluro life jackets - we absurdly enter the inky water of our own volition. I am terrified. Perhaps it's my love of B-grade monster films that lets my imagination run wild, but there are real predators in these waters. Mike assures me that there is no danger.
"The dolphins eat all the fish that other predators like," he says. "They don't come here because there is no food left. The dolphins chase them away from their territory." I was not reassured.
The father of our Danish diving companions said something to his family that clearly ended with "Anaconda". I scold him, and he jokes that he didn't realise I spoke Danish.
The trainer wades in with us and, as we bob nervously, holds out a small fish to lure in the beasts. We don't feel the water move, yet a long pink snout with little pointed teeth begins to slowly emerge from the darkness, reaching up for its treat. We watch in awe at its strange, almost polite approach to the snack, and its total invisibility until that point, realising that there are likely more nearby.
Soon enough, we are surrounded by 5 or 6 dolphins, swirling around us, nudging us playfully, even dallying with an inflatable ball, emerging for a moment to snatch it, only to release it back to the surface with a 'pop' in surprise new locations. One swims just beneath me and stays there as if to provide a foot stool, and another sneaks up beside me, its snout appearing between my arm and my side as if to tease me. I only scream a little.
Eventually, we paddle away from our new aquatic friends, my lips tightly sealed as I recall Mike's earlier warning that if swallowed, the water could make an Olympic sprinter out of you - to the toilet.
I entered the river a terrified novice and re-emerged enlightened, a bit grubby, with not one limb missing. As we sunned ourselves on the return journey, I silently marvel at the majesty of animals, and the importance of facing my fears, lest I ever miss an experience as magnificent as this.