3.9k swim, 180.2k bike, 42.2k run. Ugh.
Kona is like the Boston Marathon. You need to participate in qualifying events and hit the qualifying time to ensure you are worthy/limit number of entrants/minimize dying in Hawaii.
And each one is very different based on type of open water swim, quality of pavement, elevation changes / overall gain and exposure to the elements. It must be completed in 17 hours and races often start around 7am and finish by midnight.
A few years ago my wife wanted to do another Ironman, so she signed up for one in Florida - in Pensacola. She had previously done Lake Placid and Mont Tremblant - each in around 14hrs, and these are pretty hilly courses. She isn't fast, but she is very consistent with her pacing and she's mentally strong.
For Pensacola she didn't have the same amount of time to invest in training and this was just supposed to be fun goal to achieve. Pensacola is a pretty easy course with minimal elevation gain and a simple swim in a protected bay of the Gulf of Mexico. About 1-2 months before the event Pensacola got hit with a bad hurricane which damaged massive parts of the town and course route. The event was on the brink of being cancelled. At the last minute they moved it to Haines City, which is between Tampa and Orlando. This was a big change, because it's a hilly part of Florida (I didn't know that was possible) and now she was no longer doing an open water swim in the Gulf of Mexico, but swimming in a lake that has alligators in it
Two nights before her event we decide to go out to a nice Thai restaurant. She gets food poisoning and is barfing all night and bedridden the next day. She decides to attempt the Ironman anyways even though she has zero stored food reserves from her sickness. She does the swim at a pretty decent pace - something like 1:30 for the 3.8km despite the alligators freaking her out. Her transition on to the bike was the slowest I've ever seen - something like 23 minutes, when normally she's around 7-10 minutes. She gets on the bike and the wind was really strong and hills were not at all something she trained for. They ended up pulling her off the course about 1km from the last time marker, which is 150km into the bike ride. It was pretty heartbreaking to see her get pulled off so late in the event, but at the same time awesome to see how hard she tried despite so much going against her.
As a spectator, one of the coolest things about going to these events is staying there all day and cheering the people coming in at the 15, 16, 17 hour marks. I've seen people come running in at 16 hours wearing t-shirts that said they used to weigh 300lbs and this was their first Ironman and so on. Or cancer survivors, war amputees and other trials and tribulations of life. Really inspiring stuff.
She treats many clients who are elite triathletes and compete at Kona or other world championships. Many of them are in their 50's, 60's and 70's and are great motivation for people younger to see how taking good care of our health and being active, yield major benefits later in life.