Coastguard National Operations Centre confirmed it received reports from members of the public about the capsized yacht.
A spokesperson said the person on board was assisted by a nearby vessel, so Coastguard Tutukākā was not required to launch.
A witness to the rescue described the man who went to help as a hero.
Paul Baragwanath, who was watching the sea with his mother Barbara from their accommodation, said they became concerned almost immediately.
“My mum was looking out at the sea and said the yacht shouldn’t be out there – it was too windy,” he said.
Moments later, the yacht appeared to strike the reef and come to an abrupt stop.
Baragwanath called police, but the vessel soon came free.
However, about five minutes later, Baragwanath said the boat began pitching heavily before capsizing in rough seas.
Baragwanath rang police again as the situation escalated and a police helicopter was dispatched.
Before emergency services could reach the scene, Baragwanath said a man in a small runabout made its way across the open ocean toward the overturned yacht.
“He’s a very brave man because at any point his boat could have flipped.
“I think he’s a real hero.”
Police said the skipper was assessed by an ambulance on shore.
On Wednesday morning, the yacht remained upside down on the beach at Sandy Bay.
RNZ understands the search for Rimu continues.
-RNZ
