If you like the water try diving (or snorkeling) on Molkini Crater. It's the crescent moon shaped piece of land off the west coast of the island just south of Lahaina. You can see Molokin Crater from the Haleakala Crater observatory. Great fish and marine life to see there! My wife and I dove the south wall. Saw all kinds of marine life (Black tip reef sharks, turtles and all!). Another great dive site is "Joes tug boat". The only thing I cant be sure about is that it's not near Kauai. Im about 95% sure it was Maui. Sea turtles every where!