A 46-year-old man who was reported missing from a boat in Tasman Bay, near Nelson, swam to shore and walked home.
A search and rescue operation involving five boats and a chopper had been under for more than an hour when he was found safe and well about 7.45pm. He was now with his family, a police spokeswoman said.
Officers were called about 5.45pm to reports of a man overboard from a 4m to 5m (14ft to 16ft) boat in the bay, a police spokeswoman said.
The Rescue Co-ordination Centre had also been notified, she said.
Police were conducting a land search on Rabbit Island, five vessels were being used to scour the bay and a chopper was part of the search effort, a police spokeswoman confirmed.
