A 50 foot boat sank in the Marlborough Sounds early this morning after a huge fire on board which left two people needing treatment.
Fire Service southern communications centre shift manager Karl Patterson said the boat, the Aqua Luna, was reported on fire near the shore of the Bay of Many Coves about 2am.
The Picton fire brigade and paramedics went to the vessel's aid in a Marlborough Coast Guard vessel and found it burning fiercely.
Flames could be seen coming out of the vents at the water line, Mr Patterson said.
Two people who had been on board suffered smoke inhalation and were treated by paramedics at a nearby resort.
The burning boat drifted north to Chaucer Bay where it eventually sank.
The fire was not being treated as suspicious.