People are being urged to stay out of the water at Karitane and Waikouaiti, north of Dunedin, because of a large shark.
Police issued a warning about the situation, after two surfers at Karitane raised the alarm.
Constable John Paul Tremain says he does not know the exact size or breed of shark involved, but the experienced surfers described it as very large and said it actually chased them out of the water.
Mr Tremain says the shark is "hanging around" in the surf and appears to be lurking with intent.
