Incredible footage has emerged online of the terrifying moment a monster wave slammed into a group of 150 people at a popular swimming spot south of Sydney over the weekend.

A Westpac Life Saver spokesperson said 60 people were injured when a series of large and powerful waves crashed into the Figure of Eight Pools at Burning Palms in the Royal National Park around 2pm on Saturday.

Hair-raising footage showing uploaded to social media shows the moment the powerful wave struck.

In one clip, a man can be heard ordering swimmers to "brace themselves" seconds before impact, but for many, it was already too late.

Dozens of people were washed off their feet as the waves swept over the rock platform, while others scrambled to safety, screaming as they tried to outrun the wall of water.

Witnesses said the waves swept dozens of people across rocks and oyster beds, resulting in multiple injuries.

A large contingent of emergency services, including several helicopters were dispatched to rescue the injured.

One man was flown to hospital with head injuries, while two others had to be winched from the water and flown to a fleet of awaiting ambulances assembled at nearby Garie Beach where the injured were being treated.