This year's edition of the Ironman looks set to attract approximately 3,000 participants.
Johan Christiansson is one of them, but he is not exactly a beginner.
He has completed six triathlon races and participated in two World Championships, both in Sweden and abroad.
- I'm starting to feel that the body doesn't recover as well after training anymore.
I will probably do more races, but probably not full distance.
Maybe it will be a half distance or similar, says Johan Christiansson.
One last Ironman
To save his health, Johan decided that this time would be the last.
- Now I am 50 years old.
I don't know how long the body will last, so I wanted to drive one last time here at home in Kalmar, he says.
"Gratitude"
Can you describe how you feel in the middle of the race?
- There are 50,000 people standing and cheering and thousands of officials who have put in a lot of work to be able to do this.
Also the fact that you have a body that can handle it.
I would say gratitude, says Johan Christiansson.
Follow Johan's test swim before Saturday's triathlon in the clip above.