I know more than I care to about hairballs. If I leave a suitcase open on the floor, when packing for a trip or returning from one, invariably I find a hairball coughed up on my clothes, signaling some irritation with my travels. I have yet to determine if it's the cats, my wife, or some combination of the two who's sending these not-so-subtle messages. But it's my familiarity with the object in question that gives me the confidence to declare, "That's a hairball coughed up by a crocodile."

My proclamation is in response to our Aboriginal guide asking, "Does anybody know what this is?" He's holding up a fuzzy brown object about the size of a soccer ball. "Right," he answers, silencing the snickering. Then he admonishes us: "Keep those hands inside the boat at all times. That hairball used to be a wild pig."

We're in Kakadu National Park in Australia's Northern Territory. Every river, creek, and billabong around here has a sign that says: "Crocodiles inhabit these waters. Danger!" A graphic element shows crocodile jaws crunching a stick figure.

Clearly the plot line at Kakadu is more predictable than a Freddy Kruger movie: If there's trouble, the croc did it. So my connecting a crocodile to the hairball wasn't a wild guess. Harder to explain are my next words: "I want to go swimming."