A 17-year-old surfer died after he was attacked by a shark here on Saturday.   It was the second fatal attack in a week and at least the fifth in Australia this year.   Police said the teenager was surfing at Wooli Beach, near Grafton, about 600 kilometers (370 miles) north of Sydney in New South Wales state just before 2:30 p.m. when he was attacked.   The shark attack left him with severe injuries to his legs.   Several surfers came to the aid of the boy and helped him to shore for medical attention. Despite CPR efforts to revive him, he died at the scene.   Last Saturday, a 20-year-old scuba diver who was spear fishing died after being attacked by a shark off the coast of Australia’s Queensland state. The man was attacked near Indian Head on the eastern side of Fraser Island.   The attack happened not far from where 23-year-old Queensland wildlife ranger Zachary Robba was fatally mauled by a great white shark in April.   A 57-year-old diver was killed off Western Australia state in January, and a 60-year-old surfer was killed off Kingscliff in New South Wales state in June.