We hummed soundlessly down the Daintree River in our covered flatboat. At first the wildlife seemed to be warned of our approach and kept its distance. But as we advanced more creatures showed themselves.

With an engine powered by a battery and sustained by solar panels on the boat’s aluminum roof, we were the only craft that made no noise as we moved along the banks of the wide Daintree. No noise, that is, besides the occasional lap of water or the scream – at first intermittent, then incessant – of the small Dutch child sitting right across from us. But both the silence and the screaming proved to be advantageous in our quest to observe one of Daintree National Park’s 200 resident crocodiles: the silence for sneaking, and the screams for attracting.

It took about 90 minutes and in that time we saw plenty of other wonderful, rare creatures: a couple tree snakes, a python, a small seven-year-old crocodile resting in shallow water beneath the overhanging branches of a hibiscus tree. And the birds: the metallic starling; the sunbird; the koel; lorikeets galore; and the azure kingfisher, a sighting by Lisa that delighted even our pilot, David, who has navigated the river thousands of times and knows its every snag and mudbank.

Trips like the short tours given by Solar Whisper of Daintree offer frequent surprises even for the most experienced naturalist or river pilot. Of course, as self-taught anthropologists, biologists, botanists and philosophers, we are in a position to be surprised and delighted many different ways every day. But one of my favorite experiences is to witness someone like David, a 35-year-old with an almost child-like love for all the organic forms of the Daintree, an ecosystem with an array of plant and animal life so vast as to be nearly impossible to catalogue.

As we watched a white-bellied sea eagle torment a colony of fruit bats I almost got more enjoyment watching David’s reaction to the drama: he narrated the event in typically laconic Australian style but couldn’t disguise the undercurrent of excitement he felt in witnessing it. That kind of thing is contagious and it sustains you on a trip of this scope and duration. For days after our visit we would remember it and it would fuel us.

And that was without even the best part of the afternoon.

Afternoon is usually the worst time to try to spot a croc. We caught the final tour of the day and one of the first things David imparted was this: crocs like to sleep through the afternoon, the hottest part of the day, usually in deep, cool water. So after we spotted the youngster – who measured about a meter-and-a-half – lazing catatonically in the clear water off a mudbank, we expected no better.

It was almost enough to hear David expound on the intricacies of the mangrove biota: Daintree boasts more than 30 species of mangrove tree, one of the few places where so many are concentrated: there are only 70 species in the world. The mango trees and umbrella trees and drooping hibiscus add layers that veil the forest’s interior in a green mayhem. We slipped into reverie watching the chaotic tangle as we hummed soundlessly along the mangrove line.

Then began the screams. The child – a cute little redhaired girl – had, at first, been sedate, intrigued by the boat’s resident white-lipped green tree frog and happy to sit on her mother’s lap. Then inexplicably came the change. It happened quickly. At first I thought she must have been stung by a wasp. She began emitting a succession of bloodcurdling screams. Nothing would make her stop. A wave of despair washed over the boat’s dozen or so passengers, not least the little girl’s hapless parents.

But not David. He continued narrating in a pleasant tone about the archer fish, which gets its meals by shooting insects with spit (I threw a quick grin in Lisa’s direction), and the fact that farmers across Queensland now shoot flying foxes on sight, on principle, despite very strict laws against doing so.

Bu the problem wasn’t going away. As the little girl achieved new octaves to the consternation of all, David said:

“You know, the sound of a baby crying has been known to attract crocodiles. They are very interested in the sounds of an animal in distress.”

Just as he uttered those words we saw, not 50 meters ahead, a very large, spiny body disengage from the bank and head across the river. It was, unmistakably, the deadly prehistoric form of the crocodile. Crocodylidae: the Thunder Lizard. And a big ‘un.

“Folks, I am not psychic,” David said.

The croc, named Scarface for the evidence all over its head of pitched battles with other males, was the area’s dominant male, a 4-meter monster that probably weighed between 400 and 500 kilograms. He was around 60 years old and through the vagaries of croc life had been reduced to only about six teeth in his head.

“That does not mean he is harmless,” David said. “I have seen this one eating a cow.”

We drew close to Scarface as he swam across the river. But not too close, lest we scare him into submerging, a croc’s common response to snooping tourists. In any event we got a good long look at him, and some terrific pictures.

Strangely enough, though she seemed totally unaware of the croc’s presence (or the presence of anything beyond her fraught, ineffectual parents), the little girl chose the moment when we were closest to the croc to stop crying entirely.

I’m not saying it was her sudden proximity to the world’s largest man-eating reptile that quashed her outburst. But all creatures possess some kind of survival instinct.