Search and rescue efforts are under way to find two yachties at sea around the upper North Island after they sent out a mayday call that they were sinking.
And officials are now appealing to the public for help - to let authorities know if anyone they know out on the water is missing or overdue this morning.
The Rescue Coordination Centre New Zealand said it received the mayday via maritime radio about 6.30pm yesterday.
Search and Rescue officer Tracy Brickles said: "We understand that two people are on board the yacht but we have no further information about the yacht, or what may have caused it to take on water, at this time.
"We have serious concerns for the safety of those on board."
The location was given to be near Waiheke. But a search to find the vessel found nothing - and officials think the yacht may have given an incorrect location.
It is now believed the yacht was around the east of the Coromandel Peninsula, off the coast of Pauanui.
The Navy ship HMNZS Te Kaha has been searching for the missing boat throughout the night; while two rescue helicopters - from Auckland and Tauranga - and a Coastguard boat have also been involved.
The helicopters and Coastguard vessel were called back after searching for several hours, however, due to heavy swells in the area.
Brickles urged anyone who may have seen the yacht or has information that may help authorities to call police immediately on 111.
'All they said was they're taking on water and sinking'
Brickles also appealed to anyone who may know of someone out on the water who is overdue to return.
"We need anyone that thinks ... one of their friends is missing or overdue on a yacht because the broadcast didn't give any name of the vessel when it made the call last night.
"So we don't know who we're looking for ... It's extremely hard to search for them.
"All they said was they're taking on water and they're sinking. We don't know even if they have sunk yet."
Last night's conditions were described as very poor and rough; with 3m swells and winds gusting up to 48km/h.
The NZ Defence Force is now helping the search and rescue operation today - with a Navy crew already out on the water early this morning.
A NZDF spokesman told the Herald the C130 Hercules had also joined the search near the Coromandel. The Te Kaha and Hercules crews will search off the east coast of the Coromandel.
"A RNZAF P-3K2 Orion is also on standby to join the search today," the spokesman said.
Brickles also used the opportunity to remind people heading out on the water to remember to take safety precautions.
"When you're out on the water this summer, please take two means of communication and a distress beacon and safety gear - such as life jackets and flares that will help us to locate you."