Family Support volunteer Mel Ryall said 75 people raised $5400 to help support children with heart defects through life.
There were 180 Dunedin families who had children with heart defects, she said.
The children suffered from a range of defects which ranged from ''from a hole in the heart to what my 1-year-old son Charlie has got, which is a severe hypoplastic left-heart syndrome, which is pretty much half a heart'', Mrs Ryall said.
The Dunedin event was the third of 10 nationwide and $37,000 had been raised collectively so far.
Accident Compensation Corporation staff member Gemma Strafton, of Dunedin, said she enjoyed the crisp polar plunge.
''It's five minutes for a good cause.''