SAN DIEGO — Derek Dunfee’s dream came true, and then it almost killed him. Growing up in La Jolla, all he wanted to do was surf. He was good at it. By 13 he had a sponsorship from Volcom, the clothing company, which sent him to Hawaii’s storied North Shore, a proving ground for young hotshots. The waves were huge. Intimidated at first, Dunfee got nudged into the water by one of his idols, a Sunset Beach veteran, and found out that he loved every part of it. He loved the power of the ocean, the thrill of the tube rides, the camaraderie of the lineup. Loved being on the cover of Surfer magazine….