Fishermen are excited, but reports of a great white shark in Auckland's Waitemata Harbour come as no surprise to the experts.

Several boaties have reported sightings, which may all be of the same animal.

It's reckoned to be at least four metres long, and weigh about 800 kilos.

DOC's shark man Clinton Duffy says people should be cautious around such a big shark but it's not unusual, and isn't likely to cause problems.

He says most people don't see sharks because they don't expect to, but there are plenty moving into shallow waters, to pup and feed.