Part of a net was removed from a Sydney beach for inspection after a shark managed slip into an area where families were swimming.

Key points: Divers have searched the netted beach but can no longer find the shark

Divers have searched the netted beach but can no longer find the shark NSW Police were called to the beach around 6:30pm and closed it overnight

NSW Police were called to the beach around 6:30pm and closed it overnight Bayside Council confirmed a hole was found in one the nets

Lady Robinson Beach at Brighton-Le-Sands was closed overnight and this morning after a shark sighting around 6:30pm yesterday.

A video of the shark swimming near the shore was posted to social media by Nick Webb, who works for the ABC.

Mr Webb said he saw children and families getting out of the water in a hurry.

"I saw a bit of commotion within the swimming nets area, there was a guy walking up and down the beach alerting people to get out of the water," Mr Webb said.

"Everyone got out of the water pretty quick smart.

"Thankfully no one was injured and there was no real incident."

NSW Police arrived shortly after and cordoned off the beach.

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A spokesperson for Bayside Council confirmed divers discovered a hole in the netting on the Sutherland side of the enclosure.

They said the hole was repaired by the morning and the net was taken away to be examined.

The Department of Primary Industries (DPI) and Bayside Council were confounded by the whereabouts of the aquatic visitor who disappeared as quickly as it came.

The council said divers had searched for the shark inside the netted area, but could not find it.

Based on the video posted, the DPI said they were unable to identify the shark.

Mr Webb, a regular visitor to the beach, was concerned a shark had been found in a netted area.

"I've never seen a shark get that close to the shore and certainly not within the netted swimming area," he said.

"We know there are sharks everywhere, but it was pretty concerning."

"I think I will stay out of there today, but hopefully I'll be back in before too long."