Several Sydney beaches have been closed after a swimmer was fatally attacked by what was believed to be a great white shark at Buchan Point between Little Bay Beach and Malabar Beach on Wednesday. Emergency services responded to reports that a swimmer had been attacked by a shark at the location around 4.30 p.m., after which rescue crews found human remains in the water. A witness told 9News that what he believed to be a 4.5-metre great white shark attacked the swimmer vertically, and the splash was so huge that it looked like a car had landed in the water. “It was really bad,” he said. Another witness told Today that out of nowhere, something launched out of the water. “It was just a big shark, in the air, totally airborne, hit the guy very, very quick,” he said. “We realised it was a shark attack on a swimmer just …