At least two sharks, believed to be great whites, have been spotted just 600m from shore.
A person who was on the water and laid eyes on the pair said one was at least 5m long, measuring just a little smaller than his craft.
"We were in a 26-foot (8m) boat and alongside one of them," said the boatie who did not want to be named.
"They are very large. We came back in. We did not want to be out there, to be honest."
He said he alerted Coastguard about the danger they posed.
"We were more worried about the kids on the beach and people on jet skis," he said.
The latest suspected shark sighting happened earlier this morning as a couple on the Maraetai Beachlands coastal walkway noticed a large fin gliding at pace through the water.
"While coming back between 8-8.30am we spotted a big blue fin travelling very fast in the waters of Maraetai towards Omana Esplanade," said Deepali Kohli.
She said it was possible the threat was far broader than Eastern Beach.
For a second day, swimmers and surfers at Muriwai Beach have been warned of a new threat after the popular Auckland west coast beach was cleared due to a shark sighting yesterday.
An alert was posted on Auckland Council's Safeswim website this morning, advising against swimming at Muriwai Beach.
It said sharks had been sighted and to exercise caution.
