Waikato authorities say they are alarmed at the numbers of people flouting national direction by going out on the water in boats and other vessels.
Boat ramps are closed and signs are up advising people not to go out during the lockdown because ramps are a non-essential service.
Waikato Regional Council's harbour masters have reported seeing people in launches and yachts, some trailer boats and kayaks in waters off the region's east and west coasts in recent days.
"Boat ramps remain open for the sole purpose of enabling commercial fishing vessels and boats like ours to go onto the water," said Waikato Regional Council chief executive Vaughan Payne.
"They are not for recreational water users wanting to escape lockdown."