Concierge.com's insider take:

Contrary to popular belief, there's good surfing on the Big Island, mostly along the west side from Kawaihae to Captain Cook. The problem is that the breaks aren't easy to access. Two (often crowded) exceptions to this rule are Banyans, clearly visible from Kona's Alii Drive (just south of the Kona Bali Kai Hotel), and Honolii, visible from Highway 19 about five minutes outside of Hilo (turn into the Alae Point community and drive down toward the water). Highly skilled wave riders should seek out Pine Trees on the Kona side of the island off Highway 19: Take the dirt road near mile marker 94 (you'll need a truck or 4WD) to the Natural Energy Lab, then follow the dirt road off the parking lot for about a mile until you see the break—there actually aren't any pine trees to mark the spot. Visitors should bring drinks and snacks to share with the territorial locals. For newbies, Kahaluu Beach Park in Kona is one of the best spots for beginners and surf lessons.