VIDEO: “Run” yells father as freak wave swamps lagoon

Footage has emerged of a man being knocked down by a freak wave.

The incident, at Manly lagoon in Sydney’s Northern beaches, came as wild weather caused hazardous conditions at beaches across Australia’s east coast.

“Boys, come back quick,” another man can be heard yelling as another beachgoer attempts to unsuccessfully outrun the tsunami-like wave.

University of New South Wales professor Rob Brander, a coastal geomorphologist in the School of Biological, Earth and Environmental Sciences and the UNSW Beach Safety Research Group, told News.AU that the unusual situation was sparked by several factors.

“The recent large swell and resulting beach erosion along Sydney’s coastline was caused by a number of factors,” Brander says.

“We’ve already experienced multiple storm and erosion events over the last few months due to La Niña, leaving beaches depleted of sand. This most recent event triggered a significant storm surge with higher water levels reaching much higher than usual due to the strong onshore winds coupled with a low pressure system.

“The sudden destructive uprushes of water we witnessed were examples of ‘infragravity waves’ (or ‘sneaker waves’ in other parts of the world).

“These infragravity waves are generated by large storm waves that release immense amounts of energy into the surf zone. The danger of infragravity waves is their unpredictability.

“Once in the surf zone, these waves can fluctuate – both in ‘force’ and ‘frequency’ – on the order of minutes. One minute, these waves will recede from the shoreline with pronounced backwash, lulling beachgoers into a false security, before shifting in the next minute to sudden and dangerous uprushes.

“Infragravity wave surges occur during all wave conditions but are amplified during storms – the bigger and messier the waves, the stronger and farther the surge rushes up the beach.”