Wailua River — Hawai'i | Shared Latitude

Hawai'i's only navigable river — kayaking to hidden waterfalls, ancient heiau temple sites, and the Fern Grotto's dripping green cavern.

Hawai’i’s rivers are mostly short, steep, and unnavigable — volcanic islands don’t produce the kind of long, lazy waterways you’d paddle for hours. The Wailua is the exception, and it’s the reason Kaua’i’s east side has a kayaking culture that doesn’t exist anywhere else in the state. Lia found the outfitter through a recommendation from our guesthouse host, a woman who insisted, with real conviction, that we not leave the island without doing it.

Paddling Past the Heiau

The lower river winds past a string of ancient heiau — Hawaiian temple sites, some still marked by low stone platforms half-swallowed by jungle. We paddled the main stem for close to two miles, passing Hikinaakala Heiau near the river mouth and, further up, the more secluded sites that require a guide or genuine local knowledge to find at all. The water was flat and the current gentle enough that we mostly just drifted, watching kingfishers work the banks and feeling, more than once, like we’d wandered into a different century.

Ancient stone heiau temple ruins on the jungle bank of the Wailua River, partially overgrown with ferns and vines

Secret Falls and the Hike In

We beached the kayaks at a small landing and hiked twenty minutes through mud and root-tangled forest to Uluwehi Falls — better known, accurately, as “Secret Falls” — a wide curtain of water dropping into a swimming pool ringed by volcanic rock. It wasn’t secret in the sense of empty; a dozen other paddlers had made the same trip. It was secret in the sense that nothing about the approach — the highway, the marina, the placid lower river — suggests that something this dramatic is hiding twenty minutes upstream and on foot.

Uluwehi Falls, also known as Secret Falls, cascading into a swimming pool surrounded by lush volcanic rock and greenery

The Fern Grotto, the Easy Way

For those unwilling or unable to kayak, a river barge company runs a short, slightly kitschy cruise up to the Fern Grotto — a natural lava-rock amphitheater draped in hanging ferns that, before a 2018 hurricane, hosted actual wedding ceremonies inside the cave. Storm damage has limited close access since, but the barge ride itself, complete with a ukulele player performing the Hawaiian Wedding Song, is a strange, sincere little piece of old-school Hawai’i tourism that I found myself enjoying more than I expected to.

When to go: Year-round, though water levels and clarity are best from late spring through fall. Book kayak tours in the morning to beat both the afternoon heat and the rain that tends to build over the interior later in the day.