As soon as Isaac realizes he can handle the tumultuous terrain better than his parents, he is off leading the way, splashing forthrightly into puddles we daintily try to skirt. "Surrender to the mud" is his advice, and we soon realize how sage it is, since attempting to step along the slippery edges of these quagmires all but guarantees we'll slide in. The trail is full of children speeding out in front of their parents; you catch up at the next stream or waterfall, where the kids pause to cool off and shed a few pounds of accumulated muck.
This might not sound like your idea of fun (or, for that matter, responsible parenting). And I haven't even mentioned that it rains on and off the whole way, or that we have to ford a rushing river two feet deep before finally reaching the beach, or that we permanently retire our sneakers at the end of the day. But Isaac will tell you that this is the best hike he's ever taken: "It has everything I love: mud, rain, rain forest, and ocean." My own favorite parts are the lightning changes rung by the scenery as it turns on a dime from shadowy jungle to commanding prospect, from blinding floods of sunlight to, well, floods.
When we get back to the resort, Isaac surprises us by announcing that he wants to go snorkeling, something he's never tried. This is a kid who ordinarily only likes to do things he has already done before, so I'm not about to discourage his newfound adventurism. We've heard that Puu Poa, the resort's beach, is protected by a reef that offers some of the best and safest snorkeling on the island. (Many beaches here have dangerous currents.)
We've heard right: the water is crystalline, the coral is painless to touch, and the shifting schools of fish arrive in colored waves like turns on a kaleidoscope. Through Isaac's mask I can see his face, and it is beaming. After finally dragging himself out of the water, shivering and happy, he has one question: "So what's on tap for tomorrow?"
And that's the kind of week we have, a series of near daily "adventures," most of them involving water. Isaac haunts the rack of brochures in the hotel lobby, and we spend a small fortune on outfitters and guides. We almost never do this sort of thing (just hearing the phrase adventure travel makes me want to reach for an umbrella drink), but I've come to see kayaks, zip lines, and even helicopters not as gimmicks but as kid-friendly methods of plunging more and more deeply into Kauai's astounding landscape.
Our third morning we kayak along the Wailua River, which spills into the Pacific about halfway up the island's eastern coast. After dodging river traffic for the first mile or so, our guide leads our group of maybe 12 up a tranquil tributary. With its banyans, ficus trees, and deep carpets of fern, the scene feels weirdly primordial: you half expect to glimpse a brachiosaur lifting its head above the forest canopy. (Perhaps that's why Steven Spielberg filmed much of Jurassic Park here.)
After an hour of paddling, we beach the kayaks, cross the swollen river by clinging to a rope stretched across it, and trek through a mile of astonishingly lush—and astonishingly muddy—jungle on the way to our lunchtime destination, a towering waterfall where the kids shower off in what looks like a five-story curtain of light.
On a sunbaked boulder beneath the thundering falls, I think about Kauai's great theme: water. Basically the island is an elegant contraption for extracting water from the trade winds and recycling it back into the Pacific—but not before using it to grow flowers, carve canyons, build waterfalls, and generally beautify itself. Kauai was the first in the series of volcanoes that once upon a time sprang up from a vent in the Pacific floor to create the Hawaiian archipelago. Think of that episode of island-building as a terrestrial challenge to the watery status quo; the water has been working ever since to erase these upstart islands, and is further along in that project on firstborn Kauai than on any of its siblings. The moist trade winds bump up against Kauai's highest mountain peaks, which causes the clouds to drop 37 feet of rain every year, and as all that water works its inexorable way back to the ocean, coursing down the island's rivers and streams and bounding over its falls, it is slowly but surely bringing the island with it. It might take another million years to wash Kauai away completely, but that's the plan. (And I was worried about overdevelopment!) Once we realize that we (like the island) have no choice but to yield to the water, Kauai's occasionally torrential rains, which never last very long, stop feeling like an affront to our vacation.
Yet in the south, where we spend the latter part of our stay, you can pretty much escape the downfalls. Here, in the rain shadow of the interior mountains, the terrain is not nearly so spectacular. But the Hyatt Regency Kauai in Poipu does its best to compensate by simulating a tropical landscape with a riverine pool that meanders among ferns and flowering ginger on its way to an elaborate two-story waterslide, which Isaac pronounces "hellatight"—at the moment the highest praise a kid from California can bestow. In addition to the resort's two lovely pools (one is restricted to adults), the Hyatt also has a five-acre saltwater lagoon with a white-sand beach and palm-studded islands.