SES say floodwaters 'not a nice place to play'

As flood activity worsens across large parts of Sydney, emergency authorities are warning of the dangers when playing in floodwaters.

Concerning vision has emerged of people swimming, riding boogie boards, bikes and jetskis through the flooded Northern Beaches.

SES said children have lost their lives by playing in floodwater in previous natural disasters.

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"Floodwater can be deeper and flow faster than it looks on the surface," the service said.

"It can also cover drains and eroded surfaces that you cannot see.

"Sometimes water can suddenly move through hidden drains and pipes, and there can also be snags and other things in floodwater which can trap you underwater.

"Floodwater can also contain waste, poisons, dead animals, garbage and sewage. It is not a nice place to play".

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SES Commissioner Carlene York said it is important people follow emergency service orders.

"Listen out for your risk and make sure that you don't put yourself or your family at risk and by following what we say, our orders, you don't put my emergency service volunteers and other partner agencies lives at risk as well," she said.

"Never walk, drive, ride through floodwaters. If it's flooded, forget it."

For emergency help in floods and storms, call the NSW State Emergency Service on 132 500. In life threatening situations call triple zero (000) immediately.