The last time Chris (59) had swum in a race was 45 years ago when she was a pupil at St Philomena's school in Dunedin.
The idea of swimming at the Masters Games developed one weekend last year when Chris and her husband, Phil, visited family in Dunedin.
''We thought it would be a good time for a family reunion in Dunedin,'' Chris said.
The family reunion did not eventuate but Chris felt she was committed to competing in the Masters Games swimming.
''I had swimming lessons for stroke correction because I hadn't swum for 45 years,'' she said.
''As soon as I had the lessons I was committed to it, and to Cathy, because I knew how much she wanted it. She has been my inspiration.''
Cathy McKersey (54) would not let her older sister renege on the deal and helped her get over a series of mental blocks that could have stopped her return to the water.
''Last Friday, she taught me how to dive off the blocks,'' Chris said.
''That was a barrier for me to get over.
''I really love it now and go swimming five mornings a week before work at the Graham Conlon Centre in Christchurch.''
One day her lane was busy so she went aqua jogging and met ''an amazing group of people''.
Chris was a member of the Kiwi Swimming Club when she was at school before she stopped swimming at the age of 14.
''I played netball and other things took over,'' she said. ''I used to hate the things that went with swimming like the wet togs.''
But she has found it easier since coming back into the sport.
''I've got my bag with the swimming gear and head to work. I really enjoy it,'' she said.
Cathy is no stranger to swimming because she swam at the 2006 and 2008 Masters Games in Dunedin.
She has swum in fits and starts over the years, but she was prodded into becoming more consistent after having a health scare last year.
Swimming has helped both sisters tone up and Cathy's health has improved.
''My doctor said I was her model patient,'' Cathy said.
''Exercise is so important and it was a lifestyle choice for me.''
Cathy has noted a big difference in her sister.
''Chris has toned up and has met all these wonderful people at the pool,'' she said.
''It's the social side of it as well.''
The two sisters are close and have done many things together over the years.
''We like to have challenges and goals and having fun and keeping healthy,'' Cathy said.
Chris admitted being nervous about her race all day.`'But I felt calm when I got to the pool,'' she said.
''It was a bit scary on the blocks.''
It was a successful return to competition this week, Chris winning the gold medal in the women's aged 60 to 64 grade 100m backstroke in 2min 18.45sec and the silver medal in the 50m breaststroke in 1min 01.98sec.
Cathy was second in the 50m breaststroke in the women's aged 50 to 54 grade in 54.34sec.
''I feel a sense of achievement, not from the winning but from the participation,'' Chris said.
Cathy described her feelings about her sister's first swim in 45 years.
''I feel like a mother whose child was going to school for their first day,'' she said.
''Chris was so nervous all day.''
Chris is the head of a sporting family. Her husband, Phil Olsen, played premier rugby for Dunedin and her son, Richard, won the senior men's 1500m title at the New Zealand athletics championships in 2007.
''They are thrilled for me,'' Chris said.
''They said, `All your hard work has paid off, Mum'.''
Chris has now earned the right to ''join the boys'' at the Olsen Christmas Day morning golf challenge.
Cathy has firm views about the value of training for the Masters Games.
''People just need to get out and do it because it benefits them in so many ways,'' she said.
