The end of Australia’s long summer school holidays usually draws crowds to the beach but a spate of shark attacks in the country’s most populous state has triggered warnings to stay out of the water.

Authorities warned that recent rainfall has left the water off area beaches murky, which increased the risk of bull shark attacks.

Australian police are investigating whether a woman found dead on a popular beach was killed by dingoes, as a recent spate of shark attacks prompted officials to close dozens of other beaches on the c

The fourth episode occurred on Sunday afternoon, when a shark bit the legs of a boy who was swimming with friends in Sydney’s east. The authorities have said that the boy, who is believed to be 12 or 13 years old, was “fighting for his life.”