The police and harbourmaster are responding to a report of concern for a person seen on a yacht near Matakana Island.
A police spokeswoman said a boatie on another vessel reported about 3.40pm that a yacht with its engine running had been idling all day near Panepane Point.
When the vessel passed the yacht the person "believed they saw someone lying on the back deck".
She said about 4.15pm that a police unit was heading out with the harbourmaster to investigate.
Panepane Point is at the southeastern end of this island, closest to Mount Maunganui.