In a swimming forum I frequent, I brought up my DNF rate to a beginning marathon swimmer. It just so happened that Saturday’s Beavertail 10K broke me out of the 50% DNF rate, to a whopping 44%. (DNF’d 4 of 9 swims I’ve attempted at 10K or longer.)
In response to my comment, another swimmer, a very novice open water swimmer/wanna-be marathon swimmer (N.b., he is 1 for 1 in marathon swims he’s done) responded thusly:
44% DNF rate?! I would have already given up the sport.
That surprised me. And made me think. What would make someone want to quit this wonderful sport? Would my interlocutor not have said it if my DNF rate were closer to 10%? 20%? What’s the number?
First, what is the equivalent to a DNF in other sports? If a (running) marathon and a 10k swim are roughly equivalent, let’s look at that event for comparison: How many marathoners DNF their marathons?
Forbes did “the numbers” for the 2018 NY marathon. Fully 99% of runners completed that marathon. Now, the 1% who did not is +/- 500. That’s a lot. But still, 99% of runners completing a marathon is great!
There is a course time limit for the NYC marathon, based on when the last of the 50,000+ runners start the marathon:
In the interest of safety…race courses will remain open to all participants who are able to maintain a 13:45-per-mile pace (based on the time when the last runner crosses the start line). Those participants who are not able to maintain this pace should be aware that fluid stations…may not be available, and participants in races staged on city streets may be asked to move to the sidewalks. Late participants will be able to cross the finish line, but they are not guaranteed to be timed and recorded as official finishers.
By contrast, not many marathon swims allow the swimmer to “move to the sidewalks” or continue after the “last [swimmer] crosses the start line” as long as they maintain a certain pace. For comparison, Boston gives everyone six hours from when the last runner crosses the start line. That’s almost 14:00 per mile pace; equivalent to 58:00 per open water mile. But that 14:00 per mile is not including the minutes until the last runner starts. And those minutes aren’t trivial. The first runner wave starts at 9:32 am. The final wave starts on or about 11:15. So that makes the minimum run pace per mile just over 17:00, or the equivalent of an hour and 12 minutes per open water mile. I don’t know of any marathon swims with that kind of course time limit!
For that matter, in a marathon, if you get tired, you can walk and still make progress along the marathon’s route. The closest you can get to this in swimming is if you just happen to stop in water that is moving in the same direction as your swim route. Same with a bike race: if your legs get tired and you want to stop pedaling for a bit, you can plan it on the down-half of a hill, or even on a flat if you’ve got the speed. The only equivalent of this is the push a swimmer gets when going with the current. But in that case the swimmer is still stroking, so it’s not the same as a biker just sitting and resting his/her legs.
I think there are two major reasons for DNF in marathon swimming: a) speed (course time limits) and b) preparation (leading to injury preventing you from completing the distance). Frankly, that’s probably the reason in running, too. So let’s look at my 4 x DNFs.
- Swim for the Potomac 10K. Marathon swim #2. Distance completed: 8750m in 3:15. DNF classification: preparation. I had one more lap (1250m) to go, but only had 6 minutes left in which to swim that 1250. However, I wouldn’t classify this DNF under speed because the issue that slowed me down was my lower back. I did the first 5k in 1:35, leaving almost two hours to do the second 5k. I was ill-prepared to swim the distance, physically. After this swim I worked on “more time horizontal” to help get my back used to so many hours prone. (In comparison, marathon swim #1 was the Dart 10K, swum in a river with wonderful current, which only took me 2:35. Not long enough to put my lower back through the stress.) In fact my “time horizontal” worked as I had marathon swim #3 a month later and did great. (Swim the Suck, 10 miles, 4:44.)
- Ocean City Swim, 9 miles. Marathon swim #4. Distance completed: 4.1 miles in 2:30. DNF classification: preparation. Too cold. Salt water issues. Some very slight race logistics issues, but DNF 99% my fault. Learned that for any future salt water & cold water swims, I need to acclimatize.
- Issyk Kul crossing attempt #1, 13.5km. Marathon swim #5. Distance completed: 4.7km. DNF classification: preparation. No course time limit as this was a swim of my own making. Cold water and elevation (5100 feet above sea level) did me in. 13C throughout and I couldn’t pee nor could I take any liquids after like the third feeding. I learned a couple things. For one, I need to sked this swim in July or August when the water is warmer. Number two: I need to get some cold(er) water training in. (Happy to report to new readers that I did successfully cross the second largest alpine lake in the world, only the second person ever to have done it, less than a year later in July 2016!)
- 20 Bridges, 28.5 miles. Marathon swim #7. Distance completed: 7+ miles, then 20+ miles. DNF classification: preparation and maybe speed? So first, for new readers I’ll explain the distances I listed there. I didn’t make it through the East river before the tide changed directions and started swimming in place/backwards. They gave me two options: quit, or be moved a mile up and continue, but the swim not counting. I of course didn’t quit. When I restarted, I swam again according to the rules for a bit over 20 miles. I say DNF for prep and speed because: If I had a faster pace during the first two hours, I could have gotten far enough into the East river that the change of current wouldn’t have affected me so much. I say preparation because if I’d done more reading and consulting with other experienced swimmers, I would have known that you gotta really push like crazy the first few hours to beat that river. I learned so much from this swim, and I really should count it as two marathons because according to the Garmin on the kayak, I did over marathon distance for each half! (No, I don’t count it as that.) The second half still counts as the longest in both miles and time that I’ve gone swimming (20 miles in 6:20).
So those are my four DNFs, out of nine marathon swims. I have one DNF in a 5k which I’d put down as speed. The current in the river was so strong I just couldn’t do the requisite laps before the cut-off. This is upsetting to me because 5k is my favorite distance. But, again, I learned something!
So to Michael, the commenter who simultaneously wants to be an elite-level swimmer in only two years (after only starting open water swimming this year) and would quit the sport after a few DNFs: I hope you read this and reevaluate. This is a great sport and community. I’ve rarely met more supportive people.