A warning's been issued to swimmers, after great white sharks have been spotted in a Waikato harbour

Footage posted to a local community page, reportedly taken near the Kawhia Harbour wharf, shows a great white shark circling a fishing boat.

In a Facebook post, the Department of Conservation confirmed there's been sightings in the area, which isn't uncommon for this time of year.

It says to avoid swimming in areas where sharks have recently been seen and to calmly get out of the water, if you spot a great white.

This follows, a commercial diver being killed in a shark attack near the Chatham Islands, last month.