As the sea level peaked around 9.50am, curious swimmers and surfers took to the water in coastal areas, where there was normally land.

Beachside pools were covered by seawater and in most areas there was less sand than usual.

While locals would have recognised the difference in sea level, tourists at some coastal vantage points failed to recognise the significance of the view.

Still, the CSIRO said the tide was the highest in 18 years.

The difference between the high tide mark, and the low tide at 4.40pm, was 2m.

This compares to an average range of around 1m for the South Coast.

CSIRO researcher Kathy McInnes said the king tide was a glimpse of what coastlines could look like in around 50 years.

"By 2060 to 2070 we could be experiencing tides of at least this magnitude every month, rather than just twice a year, due to climate change induced sea level rise," she said.

Observing the king tide could assist communities to plan and prepare for the effects of climate change, she added.

"This king tide is not caused by climate change, but it can help us picture what our coastlines might look like in the future."

To this end, the State Government, along with some councils and community groups, co-ordinated a photographic survey of the king tide.

The Nature Conservation Council of NSW called for greater recognition of climate change in planning policy.

Representatives from Port Kembla Port Corporation and Port Kembla Coal Terminal said their operations had not been affected by the king tide.

But if the event did make any difference, it wasn't for the best. Fishermen around Lake Illawarra believe the king tide may have made it easier for the shark responsible for yesterday's attack at Windang to come so close to the shore.