A rescue chopper is responding to a water incident that's left a person critically injured in Te Anau.
The incident was reported at around 4pm and St John confirmed an ambulance attended the scene.
This summer has been worst so far for drownings in New Zealand since 2015, according to Water Safety New Zealand.
As of January 3, there had been 22 drownings across the country since the beginning of December, with another two months to go before the end of the summer reporting period.
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Last summer, 25 drownings were recorded across the whole three-month period, which is also the average over the past five summers.
Twenty people drowned in the month of December 2021, more than double the figure for the previous December, when there were nine.
Water Safety New Zealand chief executive Daniel Gerrard said the uptick in fatalities was "unprecedented".
"We have to start making some of these calls ... this is the worst we've had the last six years," he said.
"We're up to 22 and we've still got two months to go ... last year was 25 total so there's absolute alarm bells."
Gerrard said a common theme in drownings was people underestimating the conditions and overestimating their ability, but wondered if lockdown restrictions last year had accentuated this further.
The months-long lockdowns for Auckland, Northland and Waikato may have encouraged people to try things they hadn't done before, overestimate their fitness or delay the servicing of equipment.