"I was watching the stormy weather ... I looked out from my deck and saw the boat sinking."
She said about half of it was underwater at that point.
She said the boat was at the Salisbury wharf end of Pilot Bay and estimated it was about 20m offshore. It was "really windy and choppy with big waves" on the water.
Items from the boat were washing up on shore, including fish containers and life jackets, she said. The boat had a small cabin and was regularly moored in the Bay.
She believed no one was on the boat.
A Bay of Plenty Regional Council spokesman said the harbourmaster team was aware of the incident and were working with the owner who was on their way.
Harbourmaster Jon Jon Peters said the 7.9m boat had sunk on its mooring.
There was no evidence of oil in the water and an investigation into what caused the sinking would be carried out.
Debris from the boat has been collected from the shoreline.
Due to high winds, there was no possibility of refloating the boat over the next couple of days, Peters said.
Metservice meteorologist Mmathapelo Makgabutlane said winds peaked between 1pm and 2pm with gusts measuring 81km/h or 44 knots, according to monitoring at Tauranga Airport.
For winds to be gale-force, they need to measure between 33 and 46 knots.
"They are strong westerly winds which are pretty strong. They were quite a bit above the average wind which was 55km/h."