Two kayakers are dead and nine others have been rescued from Lake Tekapo in Canterbury.
Emergency crews were called to the lake at about 4.30pm but the police said the group of 11 may have been in the water for an hour.
Mid South Canterbury Area Commander Dave Gaskin said the two kayakers who died were young overseas tourists.
The remaining members of the group have been taken to Timaru Hospital, suffering from hypothermia, and are expected to be interviewed tomorrow.
Inspector Gaskin said the group hired the kayaks and took them out themselves, without a guide.
He said it seemed the young visitors were caught out by a strong wind.
"They got into difficulty when they'd unexpectedly been hit by a strong wind, and they'd been pushed further out into the lake," he said.
"We think they were in the water - they'd been swamped, and they'd come out of their kayaks - and they'd been in the water for up to an hour."
He said some members of the group had managed to make their way to the island in the middle of Lake Tekapo.
The names of the two people that died will be released once their families overseas have been informed.
The police described the deaths as a tragic accident.