"It was just huge, so huge, and we both couldn't speak for a little bit ... it was about as wide as the bonnet of my Nissan Cefiro - this thing was Jaws material," Mr Grant said.
Another person reported spotting the same shark that evening while surfing near Mt Maunganui.
Department of Conservation shark expert Clinton Duffy said it was "very possible" a great white was prowling the Tauranga coastline.
"They've been seen there before - in fact, there were quite a few sightings I was able to confirm as white sharks in the Bay of Plenty last year."
Mr Duffy said there were reliable reports from the Bay of Plenty of great whites close to 6m long.
He asked that further sightings, preferably with photographs, be emailed to sharks@doc.govt.nz
MONSTER WATCH
* A 5m great white shark dubbed Brutus was spotted patrolling the Bay of Plenty for several weeks in the 1990s.
* The 6m "Taranaki Terror" grabbed headlines nationwide in 2004 when it lunged at a small runabout off Waitara, leaving teeth marks in its hull.
* A great white that cruised past children on sea biscuits on the Coromandel Peninsula last summer was so large that one fisherman said people looked like bait next to it.