Today's Sunsmart Ironman Western Australia was cut back due to a shark sighting.
Some competitors were in the water when the race helicopter spotted a 2.5m shark in the area.
After 7am, the confirmation that both the full ironman comp and half ironman, along with the team competitions, would cancel the swim leg and start from the swim exit.
This turns the race into a duathlon, with a 180km bike leg and 42.2km run.
Race commentator Simon Beaumont told WAtoday.com.au common sense prevailed, despite some confusion.
"All of a sudden we could see all the boats, the rescue craft and surf lifesavers come charging towards us with a whole pile of people on board - a whole pile of pink hats," he said.
"They probably pulled about 80 or 100 people out of the water and I think people picked it almost straight away that something had happened.
"The decision was made by water safety to get the remaining swimmers out of the water ... from there, the decision then had to be made about the team event which was due to start about a hour and a half later, and the City of Busselton and race organisers chose to keep the beach closed - so no team swim."