1. HIKE: Choose from coastal beach walks and jungle treks—or do both at the same time on Kauai's Kalalau Trail. Hikes range from family strolls to full-on treks, and include all the popular trails as well as places you will have virtually to yourself. All the Islands have excellent trails, including populated Oahu.
2. BIKE: Take a leisurely bike path or go for the gusto into a tropical forest, like this one among many on the Big Island's Stainback Highway. (Renting a bike is a cheap thrill.) Kauai and the Big Island are the choices for cyclists.
3. SNORKEL: Tour boats anchor in Maui's Coral Gardens, but you can flipper there on your own as long as the surf's not up. All the islands have excellent snorkeling, although Maui and the Big Island have more of the state's top spots.
4. SURF: Listed are all the breaks for all levels, including places to stand-up paddle (SUP). The best places to be a spectator are included. You will want to seek instruction (listed in Trailblazer guides) if learning to ride the waves. Kauai, Oahu, and Maui have good beaches for beginners.
Trailblazer Travel Books are brimming with ideas, both outdoor sports and all the cultural attractions. There's lots to do. Get a copy in advance of your trip and then break out the yellow highlighter. Once in Hawaii you'll be ready to take the plunge.