The Blue Pool is a little known spot on the southeastern tip of the island of Maui. It is absolutely gorgeous, but difficult to find. Directions in Hawaii are generally a bit obscure in any case, but to find the blue pool, you need to either find a guidebook with good directions, or find a native who knows its location.
Once you know how, the path is reasonably simple. There is a dirt road about three miles (five kilometers) long leading off of the Hana highway toward the shoreline. The road curves down past a state park, through several small plantations, and through a couple of creek beds before terminating in a small flat dirt parking area. There's often a grizzled old man sitting there looking out toward the ocean. The parking here is pretty safe, unlike other areas on the island where you can find freshly broken safety glass on the ground at most any remote tourist attraction. (The common advice is to take your valuables with you and leave your doors unlocked and the windows down. If the thieves can see nothing's there, they will leave your car alone.)
After you park, you must wade across a shallow inlet by the ocean shore, and hike about 300 yards/meters up the shoreline over a field of small boulders. A quick climb about ten feet up over a larger pile brings you within view of the pool, and a climb down the other side brings you to its edge. The pool is about 100 feet (30 meters) across, and 10-15 feet (3-5 meters) deep. It is perpetually filled by a wide waterfall comprising the entire island-side of the pool. The water plummets from a high cliff, and keeps the pool brimming with frigid water. (Other things often plummet as well, including sticks, fish, and small boulders, leading most competent guidebooks to mention that it's not really a good idea to sit under waterfalls like the naked women in Tarzan movies tend to do.)
The view from the huge boulders edging the pool is nothing short of spectacular. The bright blue sky on one side with the sun glimmering off the crests of the waves contrasts with the rugged beauty of the black lava-rock wall towering over the pool on three sides. The roaring of the water cascading down the full width of the cliff competes for your attention agains the waves breaking on the boulder-strewn shore.
Anyone who makes it to this natural wonder is obligated to enter its icy waters if only to say they have done so. A swim across the entire pool from boulders to the base of the falls under the surface, while looking down through the crystal-clear water at the shining fish and the head-sized smooth boulders randomly covering the bottom, is literally breathtaking. There is no doubt after that swim that the "blue" in the pool's title could as well refer to the swimmers color after such a feat as to the pool itself. I'm still shivering.