KEY POINTS:
A female lifeguard at Omaha Beach had a lucky escape when a shark swam under her surfboard today.
Omaha Beach was closed following the incident at around 1.45pm.
Up to six sharks, thought to be bronze whalers, were spotted in the surf, the closest only 20 metres from shore.
The beach was opened at around 4.45pm.
Lifeguards patrolled the beach on quad bikes, keeping people out of the water.
Lifeguard Kris O'Neill said lessons had been learnt after a shark attack on an inflatable lifeboat days earlier.
"We warned everyone to get out, but we weren't going to take the boat out, especially after what happened the other day," Mr O'Neill said.
The latest incident comes after two lifeguards were attacked by an angry bronze whaler at Omaha Beach on Sunday.
Two lifeguards went out in an inflatable lifeboat to try and lead the shark offshore, but were instead attacked, with the bronze whaler biting into the boat causing a section to deflate.
Today's incident is the latest in a series of shark citings across the North Island, with some experts putting the sharks increased activity down to warmer recent weather.