Parts of the Sutherland Shire and St George are under water as part of this week’s king tide - the highest experienced since midwinter.
Sutherland Shire SES volunteers have been monitoring high tides at Woronora as water crosses over some roads.
Volunteers are also using the flood boat to assess and document the high tide around Deepwater Estate.
Flooding is also affecting some parts of Ramsgate Road at Ramsgate.
It is a phenomenon being felt across Sydney.
Weatherzone meteorologist Brett Dutschke said the supermoon event was "likely to have been a factor" in the high tide - the highest experienced since midwinter.
"It was forecast to reach a little bit over two metres, we hadn't had a tide that high since mid-July," he said.
"The difference back then was that high tide was after a fairly dry spell; there would have been less flooding as a result."
Mr Dutschke said the last high tide after significant rainfall was in June, but that tide occurred "a couple of weeks" after the rains.