It would have been an otherwise calm day today on the still waters of Lake Te Anau if not for a group of 80 people who briefly jumped in for a good cause.

Te Anau School's annual Polar Plunge event raises funds for its Year 6 end-of-year camp to Dunedin.

While some plungers played it safe with a wetsuit, most got into the spirit of the event by wearing brightly coloured costumes: animals, cops, superheroes, even a shirtless Donald Trump.

Most of the adults were eager to get out of the water as soon as possible, but many kids didn't seem to mind the cold and stayed around in the lake for awhile.

Kiri Bell and her son Tarn were two of some 80 plungers to brave the icy waters of Lake Te Anau today.

Afterwards, plungers were treated to a free hot chocolate at the Te Anau Marina.

The total funds raised for the event were still being tallied.

However, Te Anau School principal Grant Excell said at least $4,000 had been raised from the raffles on offer, and the event's "celebrity" plungers (well-known residents of Te Anau) had raised a total of $700 on their own.