Emergency services were called to Coogee Beach in the east of Sydney, Australia's largest city, in the morning on reports that the 30-year-old had been bitten, police said in a statement.
"The woman was pulled from the water by members of the public who commenced first aid," police said, adding that the victim suffered serious arm and leg injuries.
"She has large flesh wounds to the leg and the arms that are going to require a lot of surgery," New South Wales Ambulance Inspector Mike Corlis told reporters at Coogee Beach.
Coogee Beach and others in the city's Randwick Council area were closed for 24 hours following the attack.
"We'll be working closely with the New South Wales government, awaiting instruction as to when it is safe to reopen," council mayor Dylan Parker told reporters.
