🏊‍♂️ From Dead Last to Course Record: The Truth About Swimming in Ironman

You don’t win an Ironman in the swim—but you swim just well enough to get to the bike. 

It’s a hard-earned truth in triathlon, proven time and again by pros like Lionel Sanders. At the 2016 Ironman Arizona, Sanders emerged 52nd from Tempe Town Lake, turning a rough start into a blistering course record of 7:44:29. The takeaway? Swimming sets the stage, but the real drama unfolds on land.

Swimming might be the first leg, but it’s the shortest—just 12% of a full Ironman. The other 88%? That’s where the race is won or lost. While the numbers sound simple, the biomechanics are anything but.

Here’s why: powerful cyclists and runners come equipped with traits that work against them in water.

Hill-crushing, muscular legs? They sink. Drag in water is up to 800 times stronger than in air at 20 mph, making streamlined form essential. Low body fat, great for power-to-weight ratio on land, turns into a buoyancy struggle.

Upper bodies built for bike aero positions lack the muscle patterns that make swimmers glide.

And Sanders? Known for his less-than-stellar swim splits but feared for his bike-run prowess, he’s living proof of a fundamental truth: swimming success has diminishing returns in long-course racing.

So, what’s the lesson? Strategic triathletes don’t skip swim practice; they master it just enough to stay in the race. The real investment is in the bike and run, where the biggest gains are made.

Next time you see a pro lagging behind after the swim, take note. They’re not beaten; they’re just getting started.