Although it's something of a tourist trap, the cruise up the Wailua to Fern Grotto is still entertaining, and the grotto in itself is lovely. During the boat ride, guides share stories of the islands, along with their musical and dance heritage. Folks are even invited to participate. The grotto is a stone formation whose moist environment provides an ideal growing environment for the fragile ferns. They cover the rock surfaces with a green cloaking that's singularly beautiful, and couples often choose to be married amid the delicate fronds.