A boat has sunk near Princess Wharf in Auckland after colliding with another vessel at the Auckland Anniversary day Regatta.
Police say a sailing boat was hit by another vessel at about 11am.
They say the four people on board were rescued by crew on another vessel in the Hauraki Gulf.
The Coastguard attended the incident.
Meanwhile, crowds flocked to the Auckland waterfront for the annual regatta, which has been a fixture in the Auckland calendar for 172 years.
Waka, yachts and America's Cup vessels were all on the water in a variety of races and displays.
Other parts of New Zealand celebrating Anniversary Day on Monday included Northland, Waikato, Bay of Plenty, Nelson and Buller.