Lumahai Beach has been photographed from almost all angles (among other claims to fame, it served as the setting for the 1957 film "South Pacific"). It's a very wide stretch of sand backed by cliffs with lush vegetation and is about ¾ of a mile long.
Lumahai sits between Haena and Hanalei Bay on Kauai's north shore and is great for picnics under the trees, photography, and wave watching.
There is no offshore reef protecting this beach, so the waves are very large and very strong. The force moves the sand around so much that it actually changes the shape of the beach itself each year.
There are no restrooms or lifeguards around and swimming is not recommended, but the scenery is fantastic and it's a wonderful place to hear the roar of the waves.
Sit back from the shoreline to enjoy the view, though, since the strong high surf can arrive quickly, break dangerously, and pull back powerfully. You might like seeing some professional (or daredevil) body and board surfers around, but keep the strong current and waves in mind before you consider joining them.
Park at the scenic lookout off Hwy. 560 just after Hanalei, then take the trail to the beach below.