Surf Life Saving Northern Region duty officer Dan Short told media outlet Newshub the shark was spotted yesterday about 500 metres offshore from Orewa Beach, twice forcing its closure.
"The shark itself wasn't showing any dangerous activity, the only thing that was actually visible was the fin coming out of water," he told the outlet.
He said there were always sharks around.
"Sometimes you can see them on a nice clear day when the sun's out and the water's nice and glassy, and other times you can't," he said.
"It's their playground, it's their home."
Those looking for alternative beaches to swim could check Safeswim for a guide to any other warnings.
Short told Newshub the warnings signs weren't a closure of the beach but a warning for anyone who did brave out to exercise caution.
"If the shark is showing any dangerous activity like breaching out of the water or chasing schools of fish, we do normally close the patrolled area at that point in time until the shark is gone," he said.
