Eons of running water are responsible for Hawaii’s escarpments and canyons. After a rainfall, innocuous streams, pools, and waterfalls can swell to impressive sizes. For an easy hike, walk along the Maunawili Falls trail on Oahu to glimpse the 20-foot cascade. There’s a lovely swimming hole, and you can scramble to a rocky overhang to dive into the pool below. On Maui, hike to the Makahiku Falls and climb to the overlook above to view two very different representations of water: the thundering 181-foot cataract below and the vast panorama of ocean beyond. Kauai, “The Garden Island,” is known for its spectacular waterfalls. The beautiful double streams of the Wailua Falls are easily seen from a roadside viewing point.