Cape Town - The National Sea Rescue Institute has warned the public to be vigilant when heading to the beach on the Southern Cape coastline after a large number of White Sharks were spotted in Plettenberg Bay.NSRI Plettenberg Bay duty controller Ross Badenhorst said in a statement that the increase in shark activity at this time of year was part of the animals' normal activity.Badenhorst said sharks were clustering in the area to take advantage of naturally occurring pray such as fish and seals. Bandenhorst asked the public to avoid swimming or other water related activities in areas where birds, dolphins or seals were feeding, where fishing was taking place, or where a whale was stranded. Additionally, he asked people not to swim when they were bleeding, when it was dark, or when they were alone. Bandenhorst said the NSRI were well prepared to deal with any incidents and all their boats, vehicles and medics carry emergency medical shark kits to ensure they respond quickly to an incident. The White Shark is the largest predatory fish on Earth.National Geographic reports that Whites were responsible for a third of the 100 humans killed by sharks annually. Great Whites are endangered, with their numbers decreasing rapidly as a result of over fishing. They are also accidentally caught in gill nets.