“Participants don't have to be a competent swimmer. . . it's a personal journey, not a competition.”
There was no start or stop point for swimmers, she said. It was about setting and achieving a goal for yourself, “whether that is 10km or 400km”.
“You're in an environment where other participants encourage each other to work towards your goal distance, whatever that is.”
Rennie competed in the 2004 Athens Olympics and the 2006 Melbourne Commonwealth games in road cycling and now owns a business that offers cardio training.
She previously competed in triathlon and said swimming was her least favourite discipline, but she is recovering from a recurring hip injury that may need surgery so she cannot run, her preferred exercise.
The low impact nature of swimming meant she could keep up her fitness and cardio while she was recovering, she said.
“It's a neat challenge to motivate you to get into the pool.”
She swam 6.5km over two sessions yesterday to complete the distance, not realising she was so close until she was told by pool manager Hendrik Geyer.
It is her first time taking part in the event and she said it was great to get in the water and train.
Rennie has no personal goal for distance but will continue swimming to help her team, The Originals, who are top of the leaderboard so far.
One of her teammates, Deb Reeves, has also likely completed the distance but she is competing out of Hawke's Bay and hasn't logged how far she has swum this week, so Rennie is the first person to officially complete the 45.5km.
Following feedback from other years, a special backdrop of Mahia, complete with sand and a bell, were created to acknowledge those who complete the challenge.
Rennie was the first to leave her footprints in the sand and to ring the bell to mark making it to Mahia.
Geyer said the event was for all shapes and sizes and was about giving it a go and getting people active and in the pool during winter.
People can enter throughout the event's duration.
This year's challenge — the 10th — has attracted a record number of over 270 participants.
Geyer thanked the local businesses who provided spot prizes for the challenge and principal sponsor Recreational Services.
If Covid-19 restrictions continue, staff are considering extending the challenge so people have enough opportunity to achieve their personal goals.