The seven people, including Bougainville Health Minister Charry Napto along with his wife and son, had left Buka for Nissan Island on Saturday morning for what is normally a three-hour trip.
The search for the missing six continues.
The man, now in Buka Hospital, said just 300 metres off Nissan waves hitting the front of the boat caused panic, prompting Napto's wife and son Keith to jump off the boat.
The National newspaper reported that the efforts to then pick the couple up caused the boat to take on water and it quickly sank.
