Council lifeguards have closed all beaches between Shelley Beach and Queenscliff Beach as a precaution following a shark sighting and shark attack on a dolphin in the area.
Lifeguards will continue to monitor the situation and will only reopen the beaches when it is safe to do so.
Council urges any beach goers at Manly to adhere to beach safety warnings and stay out of the water at this time.
All relevant authorities have been notified.