The Ultimate Swim: The 12,000 IM

The 12,000 IM. 3,000 yards of butterfly, backstroke, breaststroke, and freestyle. Has it ever been done? Frankly, should it ever be done? Alex Mathson, a senior at Carleton College, completed a 12,000 IM in the Carleton College Thorpe Pool on Thursday March 2nd 2017. It took him 2:46:58.78 to complete the ridiculous swim.

Each 3,000 yard portion of the individual medley took Mathson just under 45 minutes (Butterfly 42:23, Backstroke 43:09, Breaststroke 44:12, Freestyle 36:33). Occasionally, in the name of safety, he would stop at the wall to take a few swigs of Gatorade to keep his energy up. He never touched the bottom of the pool during these brief breaks to ensure he would not be disqualified. Mathson’s teammates traded off the roles of counting, timing, and cheering while he swam.

“I decided to do it because I had done a 3,000 straight butterfly before and figured that would be the hardest part of the 12,000”, Mathson reasoned when asked why he had even considered attempting a 12,000 IM. Andy Clark, head coach of the Carleton College men’s and women’s swimming and diving programs, called the swim “truly inspiring, very impressive, and quite utterly shocking that he swam so far”.

Have you seen any other swimmers try a historically, long swim such as this?

Check out the entire swim below.

Leave a Reply

Notify of
newest most voted
Inline Feedbacks
View all comments
4 years ago

good lord that is horrendous to think about, and I thought a mile butterfly was unfathomable *shivers*

Reply to  kaev
4 years ago

Mile fly was unfathomable? I could barely do more than a 100 fly without my arms dying haha

4 years ago

I did a 10k yard IM in 1991 in college (old bucket backstroke turns and all legal fly/breast turns in a flat, high wall pool no less). I think the choice was 3k fly or 10k free. I started to think the hardest part would be fly, so instead of doing a 3k fly why not do a 2.5k fly followed by the rest of the strokes to complete the 10k IM. It was myself and one other swimmer in the lane. We traded leads during our better strokes so that kept it interesting. My time was 1:55 (1:15 average per 100, which is now faster than I can basically do in practice for just 4 of them!). My coach… Read more »

Conger FTW
Reply to  Jeff
4 years ago

Hey what team? My old team had a similar challenge

Liz Sands
Reply to  Jeff
4 years ago

Ours was in 1989. Back in the crazy old days of “monster workouts” and “psycho day”. I miss being able to recover that quickly.

4 years ago


4 years ago

Is it odd to anyone else that there are still pools that have blocks on the shallow end of the pool?

4 years ago

Seen a 10k butterfly LCM

Top of The Day (if anyone gets that reference)

Reply to  Swammer181
4 years ago

Yup …16,000 LCM IM backwards (DW) ….Top of the Day !!

Sean Seaver
4 years ago

Yep, I’ve done a 12k IM

4 years ago

Dave Wharton is infamous for having done a 16,000 Yard IM and a 10,000 Yard butterfly sets. Not to mention his World Records and Olympic Medal.

4 years ago

12K in short pull. It is almost 500 turns. Each 15 (or so) seconds. Should they all be flip turns a swimmer would get completely disoriented and would have difficulties to get out of the pool on his own. It is a great example of lack of creativity: there are plenty of other more pleasant ways to damage your health.