Searchers looking for a missing Chinese PhD student believed to have been swept out to sea while doing research north of Auckland have found her notebook.

Yue Gui, 30, known as "Alice", was last seen at 11pm on Saturday at the Leigh Marine Reserve Faculty, operated by Auckland University, about 80km north of Auckland. She is believed to have been swept out to sea while taking ocean temperature readings on Sunday morning.

Police divers resumed their search at first light today in slightly better sea and weather conditions than yesterday, but have still had to contend with large swells, Sergeant Bede Haughey of Warkworth police said.

"There are some caverns under the rock face where the waves are breaking so they want to get in there and eliminate those areas.

"They're working around the swells and tides and some pretty jagged rocks so they've got to be careful that they don't come to any harm themselves."

A notebook believed to belong to Ms Gui was today found on rocks near to where she was thought to have been doing her research on Sunday morning.

Its pages had been bleached by the sea so no entries were discernible.

Yesterday, searchers found footwear and a beanie belonging to her in the same area.

Mr Haughey said he had heard nothing but glowing accounts of what Ms Gui was like.

"Everything that we've heard is that she was just a lovely girl who was committed to the sea and marine life and wanted to make a life here in NZ, where we're obviously strongly connected with the marine environment."

He had been speaking to her family through an interpreter every day, who were trying to arrange visas and passports to come to New Zealand from Beijing.

"Her mum's obviously quite traumatised. She was hopeful early on that her daughter was just missing but she's now come to the realisation that we're looking to recover her daughter as opposed to saving her."

A decision would be made tonight on whether the dive squad would continue its search tomorrow or whether to rely on a police Eagle helicopter doing sweeps of the coast.