50 States of Wonder
8 Watery Wonders in Hawaiʻi, Without Setting Foot in the Ocean

The last of three caves on a short hike up from the road and down a steep rocky scramble on Kīlauea, Waikapalae wet cave is also known as The Blue Room, for a secret back grotto that once glowed an otherworldly blue. The coloring was attributed to sunlight reflecting off calcite (though some have given it a more out-of-this-world explanation). The effect has diminished as the cave's water levels have dropped, but it is still visible when the tide is high and the sun is just north of Haʻena State Park. The Blue Room also made a cameo as the Fountain of Youth in 2011’s Pirates of the Caribbean: On Stranger Tides. (Read more.)

Hualālai volcano on the Big Island last erupted in 1801, sending lava to the sea and forming Keahole Point, the westernmost spot on the island. An unusual lava tube created by the flow remains intact today, serving as a conduit between the ocean and the cliff above. When waves hit the coastline just right, water rushes through the lava tube opening, blasting vertically from an opening in the coastline. Swells most consistently batter the Kona coast in winter months, when humpback whales often grace the view and offer the chance to see two kinds of blowholes at once. (Read more.)

The pristine Kona coastline of the Big Island is one of the sunniest shores in the United States. Combine that with the cold, deep-sea waters of the Pacific Ocean, and you get the ideal conditions for harvesting microalgae. So it makes a natural place for a 90-acre algae farm, where long, multicolored tanks cultivate microorganisms such as spirulina, for use in nutritional products. The lab has a visitor center and offers tours and lectures on renewable energy and marine science, but anyone can take in the stunning views taken by satellite. (Read more.)

A beautiful, 442-foot cascade in the Hamakua Coast area of the Big Island, ʻAkaka Falls carries Kolekole Stream to the rainforest floor below. And it's not just pretty. The falls also have an unusual resident: goby fish that climb up the wet rocks behind the falls. The tiny fish live in the ocean but spawn in the stream above the falls. Using a special sucker on their undersides, they scale the rock and lay their eggs at the top. The eggs are then washed back out to the ocean, where they hatch and mature, beginning the cycle all over again. (Read more.)

Among Hawaiʻi's many incredible geological formations, the Mokolea Lava Pools stand out. This partially submerged lava-ledge sits 20 feet above the sea, but incoming waves can be twice that height, drowning the ledge and then revealing a series of roiling tidal pools. Sea life is often caught in the strong tides—and photographers who flock to the site should be careful, too. (Read more.)  

Also known as the China Wall, the Spitting Caves are found on the island of O‘ahu. Ocean water that rushes into the cave is often spat back out, sometimes with a force so strong that the water looks like it has been shot out of a cannon. It's also a good rainbow machine, generating the phenomenon in the mist at the end of the water trail. It's a popular location for cliff jumpers, but take care—there's a makeshift memorial nearby for those who have died doing it. (Read more.)

This breathtaking 80-foot waterfall is located within Wailuku River State Park, itself within the city of Hilo. The natural wonder was thought to be the home of the moon goddess known as Hina. The falls are known as Waiānuenue in the native Hawaiian language, which roughly translates to "rainbow water," and it's easy to see why. Almost every morning at around 10 a.m., the falls produce a dazzling series of rainbows. (Read more.)

The ʻOheʻo Gulch is a natural playground, where beautiful tiered pools cascade through the gulch, and have been dubbed the Seven Sacred Pools. When hard rains hit, there are more like 20 pools in total. The Pipiwai Trail, located above the pools, is one of the best hikes on Maui. (Read more.)