Andrew Nicholson, who came fourth at the 1992 Winter Olympics in short-track speed skating, is advising skaters to take care as hundreds flock to Central Otago where cool conditions have frozen several lakes and dams.
Mr Nicholson shared a message on social media on Sunday after skating at the Lower Manorburn Dam the day before.
He had "swooped" a couple of metres away from a stretch of thick ice and had fallen through, his "cries unheard", but he stayed calm and managed to float to safety.
"If I did not know the drill I would not be here," he said.
Mr Nicholson told the Otago Daily Times if it had happened to someone who did not know what to do, "it could have ended very differently".
He got out "with nothing more than a few bruises", had plenty of warm clothes on hand, and within five minutes had warmed up and went on to have a "fantastic" couple of days skating.
Mr Nicholson said it was a "spectacular feeling" to glide along natural ice and did not want to discourage people from experiencing it.
"It’s just like so many activities, care needs to be taken and even experienced people like myself can get caught out."
Mr Nicholson recommended not skating alone, having equipment such as ropes and ladders handy and checking the ice was thick enough — about 5cm-8cm.
While the ice ideally needed to be drilled first, it was not always practical, and at the end of the day, "if it sounds too thin, it probably is", he said.
People should not skate where others had not, never assume the ice was all the same thickness and if in doubt not go out beyond depth, he said.
In the case of the dam, as long as people were skating over a certain area consistently and people were spread out, it was "generally safe".
One factor of the dam that made it "potentially dangerous" was an unforeseen current that ran down one side of the dam, making the ice on one side thinner, he said.
He also recommended ice skaters study on YouTube the correct procedures to follow in case of an emergency.
It is believed it was last skateable in the 2010s.
Cromwell resident Miro Kollar was skating on the Manorburn for the first time.
He played for the Alexandra ice hockey team and headed to the Manorburn after hearing from team-mates how good it was.
Mr Kollar, who was born in the Czech Republic, was skating with his children and wanted them to experience skating in the outdoors in the fresh air.
Allan Johnston, 91, of Alexandra, recalled skating on the Lower Manorburn Dam in his youth.
He was just observing the ice yesterday but "would have loved to get on it".
One of his favourite memories was skating at night, in the light of the moon, he said. — Additional reporting Ruby Shaw
