Oahu has a great bus system! Depending on where you plan to go, you might not even need to rent a car to hit the beach. (Soft boogie boards are allowed on the bus.)

Franko's O'ahu Surfing Map details over 150 surf spots on the North and South Shores of Oahu. Oahu Surfing Locations Waikiki Beach (good for beginner) (crowded): Diamond Head, Tongg's, Publics, Castle, Blowhole, Queens, Canoes ask a lifeguard Makaha (especially good in the winter) Yokohama Bay Seven Mile Miracle (Haleiwa to Sunset Beach): Rocky Point, Banzai Pipeline, Ehukai, Waimea Bay, Chun's Reef, Laniakea, Sunset Beach Kahna Bay Malaekahana Kailua Bay Wimanalo Bay Point Panic, Kahala, Diamond Head, Ala Moana Sunset Beach Waimea Bay 'Ehukai Beach Hale'iwa Ali'i Beach (free surfing lessons at the county surf center are available here on most weekends in the Fall and Winter, 637-5051) Waikiki Beach & Diamond Head Beach Makaha Beach Park Yokohama Bay Makapu'u Beach Sandy Beach