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Triathlon Swimming Technique: How to Not Sink When Swimming

by Taren Gesell

Blog ▸ Triathlon Swimming Technique: How to Not Sink When Swimming

Taren Gesell

"Triathlon Taren" Gesell is founder of MōTTIV and one of the world's top experts on helping adults become endurance athletes later in life. Best known for his YouTube channel and podcast Taren is the author of the Triathlon Foundations series of books and has been published featured in endurance publications around the world.

When you’re training for a triathlon, you’ll do a lot of swim training and spend time in the water trying to perfect your technique. The swim is a daunting part of the triathlon for many of us. There’s the unfamiliar environment of moving underwater and the amount of effort we exert to complete this part of our race as soon as possible. And there are a few reasons why we simply spend too much energy in the swim – one being sinking legs!

Sinking legs or swim legs are a common swimmer’s nightmare. So here’s a complete guide on how to not sink when swimming, from why it’s challenging to keep your legs in line with your body to how a “float like a log” body posture helps you be a better swimmer, and key drills to perfect your technique.

In this article, you’ll learn:

  • Why developing good swimming technique is tricky, and how your sinking legs cause trouble throughout your swim;
  • What great swimming form looks like;
  • The top 3 mistakes you’ll make to cause your legs to sink;
  • 7 drills that fix sinking swim legs.

Triathlon Swimming Technique: Why Is It So Hard?

As you start triathlon training, swimming is one of the critical challenges for most beginners. Despite your childhood swimming lessons or swimming for leisure, unless you’re an accomplished swimmer, the swimming part of your race can be daunting for most of us.

Why is swimming for triathletes such a challenge? 

First, water is a foreign environment for athletes in general. You’re acclimated to running and biking outside in fresh air, without any restrictions to your breathing pattern. But, in the water, we’re all essentially newborns in Speedos.

Second, swimming requires you to use your whole body in a completely different way than you use it while running or biking. To begin with, you’re not upright, and you’re not using your legs to move you forward. So, your legs find themselves in a difficult position, along with the challenges of controlling your breathing.

Once you’ve dialed in your breathing while swimming, it’s time to focus on the technical aspects of how you move in the water to float smoothly across the pool. The question is: how can you achieve a smooth, straight motion while swimming, and what’s preventing you from doing that now?

The answer lies in science. To move through water, you have to contend with four forces

  • Gravity from your body weight pulling you down;
  • Buoyancy from the air in your lungs lifting your upper body up;
  • Thrust from your swim stroke moving you forward;
  • Drag from the density of the water pushing you back.

Thrust is the only force working to your advantage, while the other three are putting up a fight. And – among all of them – the buoyancy in your lungs contributes to your sinking legs. This is because the most buoyant body part (your lungs) is at the opposite end of your body from your legs. Our bodies effectively become a seesaw, causing our legs to sink and creating even more drag. End result? You get slower and spend more energy trying to compensate for your swim legs pulling you down.

Gravity also works against you. Muscle is heavier than water, and the most muscular part of our bodies are our legs.  The buoyancy in your lungs causes a seesaw effect pushing your legs downward.  This feeling of sinking causes many beginner triathletes to get fearful and tense up, or kick rapidly to try to get their body back to the surface.  This tension and thrashing just causes your legs to sink more, creating more panic, creating more tension, creating more sinking.

Just to be clear: having muscular legs doesn’t mean you’re always going to have sinking legs! Many pro triathletes like Cameron Wurf, with a sports background, have built strong, muscular legs. In Cameron’s case, years of Olympic-level rowing and professional cycling have built strong muscles, but this didn’t stop him from exiting the water in the front swim pack at the IRONMAN World Championship 2018. Everyone can learn to float – you just need to develop the right technique.

What Does Good Swimming Form Look Like?

By now, you’re probably wondering what “floating like a log” and having good swimming form looks like, including how to get those swim legs up to the surface of the water.

Here’s what we’re aiming for:

  • Your face will point straight down at the bottom of the pool, with your eyes gazing slightly forward, the water line is at the very top of your head;
  • The back of your head, your butt and your heels are at the surface of the water;
  • Your heels kick in and out of the surface of the water, keeping your legs from sinking.

Ideally, when swimming in this good form, you narrow the channel your body occupies when looking at it from the front, making it more hydrodynamic. You also conserve energy, so you’re not burning out by the time you get on the bike on race day. Finally, the drills we’ll cover later on are designed to make all this automatic so that you can perform the proper movements under pressure.

The 3 Mistakes That Make Your Legs Sink

Okay, so you may be thinking, “All this theory sounds great, so I’m trying to implement it in my triathlon swim training, but why are my legs still sinking?”

Here are the 3 mistakes which cause your swim legs to sink:

  1. Lifting your head upward to breathe, causing your legs to go down;
  2. Kicking aggressively and with tense legs, burning a huge amount of oxygen and initiating a panic response;
  3. Kicking wide or spreading legs apart as you kick, creating drag outside the body line.

Practicing the following drills prevents those three mistakes and creates a smooth, unified motion in the water that complements the relaxed, panic-free swimming style we worked on to improve your swim breathing.

7 Drills to Banish Sinky Legs

If you’ve been working on your swimming technique and perfected your breathing with our drills that help you breathe like a dolphin, you’re ready to now elevate your kicking and leg position so that your swim legs help you float like a log across the water.

The time for folding up like a taco is over! You can perform these drills in the same sessions as the breathing exercises, and you’ll see they’re meant to complement each other. It’s all about one smooth, unified swimming motion. So let’s dive in (pun intended)!

Note: Whenever we talk about kicking drills, remember that these are not meant to propel you forward! Instead, we’re using kicks to keep ourselves at the surface and avoid sinking legs. As an age-group triathlete, you’ll never get that much propulsion from kicking… 5% if you’re lucky! We kick just enough to keep your feet at the surface of the water like I’ll show you below.

To make all these drills easier you should start out using fins and a snorkel, then progressively take away the fins and eventually the snorkel as you become more comfortable with the drills.

Drill #1: Tombstone drill

To keep your legs at the surface of the water naturally, start with the tombstone drill. For this, you’ll need to put on a snorkel and then cross your arms in an “X” shape across your chest. Go down into the water face first and then practice kicking across the pool while pressing your chest against the water.

By pressing your chest down, you’ll get a little buoyancy, so at this point, kicking really gently while activating your core makes you feel that ideal swimming position where you’re floating across the top of the water. 

You’ll know you’ve got it right when you feel the back of your head and shoulders, your butt and your heels just at the surface of the water.

Drill(s) #2-5 Kicking progression

It would be unfair to ignore the classic swimming drills involved in kicking progression. That said, I see too many people kicking vigorously instead of focusing on getting their body in a nice, smooth line to avoid those sinking swim legs.

So, as long as you’re focused on being a log, here’s how to do the kicking progression drills. First off, some general points that apply to all drills:

  • Always look straight down to the bottom of the pool. This helps your head and shoulders stay just at the water line, unlike most kicking drills that have your head out of the water – which encourages your legs to sink. 
  • Keep the back of your head, your shoulders, butt and heels touching the surface of the water.
  • Extend your arms out in front, shoulder-width apart. Be careful not to spread your arms wide and, if you’re holding a board, hold the butt-end corners of the board on the edge closest to you, not the leading edge (or rounded edge).
  • Kicking should be done lightly – imagine a gentle fluttering motion. 
  • Activate your core to stabilize your upper body. This prevents your torso from rocking back and forth.
  • Kick within a narrow channel (1.5-foot max).

Progression 1: Kick with board, snorkel and fins

Wear your snorkel, so your head never needs to get out of the water. Hold the board straight ahead of you and kick lightly from one end of the pool to the other. Simple!

But remember: focus on engaging your core and keeping that smooth, straight body position throughout, never kicking too violently. You’re aiming for a straight line from the back of the head to the heels and kicking smoothly the entire time.

Progression 2: Kicking with a snorkel and fins

Like I’ve said before, a big problem with using the kickboard is that athletes take their goggles off and lift their head out of the water during the kicking. This creates that taco fold we’re trying to avoid!

So, now, drop the kickboard and put your snorkel back on. Extend your arms over the top of your head with palms together at the front, ensuring the back of your head and shoulder, your butt and your heels are at the surface of the water. Holding this perfect floating position, kick across from one end of the pool to the other.

Progression 3: Kick with board and snorkel (no fins!)

Take the board and do all of the above, holding your head down in the water the entire time and breathing through your snorkel. This drill acclimates you to how it feels to kick in that fluttering manner we’ve talked about without the added help of the fins.

Progression 4: Kicking with snorkel only

Finally, removing the board and fins, but continuing with the snorkel, do a few lengths just kicking with your head in the water, focusing on that nice smooth body position, and on having your arms stretched out in front, in a narrow channel, the entire time. 

You’ll know if your kick is efficient when you can kick across one length of a 25-meter pool in 40 seconds. If you’re unable to do this, you’re either kicking too slowly, or you’re struggling with unnecessary drag created by a suboptimal body position and sinking swim legs. This drill will helps solve that issue.


For more kicking progression drills, including side kicking, you can check out the Triathlon Swimming Foundations book, where I detail all sorts of extra tips and tricks to get rid of those sinky legs!

Drill #6: Breathe, three strokes, breathe

Let’s say you’ve been working on your kicking, and you have a great idea of how to keep that line of the back of your head, shoulders, butt and heels at the water surface. But, once you actually start to swim and you have to coordinate using your arms and breathing, all hell breaks loose, and you lose track of the good reflexes we’ve just developed with the first two drills.

This is where this drill comes in, bridging the gap between kicking only and swimming. Put your snorkel back on, and then start kicking with your arms forward just like you did in the kicking drill. Focus on your body position throughout (remember: float like a log!). Leave one arm back and continue kicking with one arm forward, head down in the water, nice and straight.

Then kick continuously, take three strokes, then be on your side and kick again. Repeat on each side several times. The beauty of this drill is that your body position continues to be straight while you don’t have to move your head to breathe. So you can keep focusing on staying in a nice narrow channel when you’re doing your strokes, instead of any lateral movement which destabilizes you and leads to folding in the water and sinking legs. 

Think about being straight the whole time: your front arm straight ahead from your shoulder, and when you pull back, do so in a straight line. That should bring the kicking and good position altogether.

Drill #7 Fix “advanced” sinky legs

You might have done all these drills, and, most of the time, you feel like you’re swimming well and have avoided the dreaded sinking swim legs. However, there’s also something called “advanced” sinky legs… yes, you read that right!

Let’s say you’re a pretty good swimmer, and you can get around your triathlon swim in a decent time, but you’re looking to get faster, and you’re still struggling because of your bulky, muscly legs. The test on whether you have “advanced” sinky legs is: are you faster swimming with or without a pull buoy? If you’re faster with it, then read on!

When we swim is the only time when our legs should be far behind us. Think about it: in daily life, you’re sitting at a desk with your limbs in front of you. It’s the same when you bike and run, but with swimming, getting yourself into that smooth, straight line involves your legs being pushed back so they don’t create drag in the water. 

Here’s how to work on reducing your drag and increasing your speed:

  • Firstly, we’re going to return to the kicking drill with a snorkel and no fins or board… but an added challenge! When you’re in open water, you should also lift your head and look where you’re going (also known as “sighting”). This naturally forces your legs down; think of your body as a seesaw. 
  • So, as your legs are trying to sink, and you’ve lifted your head at a 45-60-degree angle, focus on bringing your heels back to the surface of the water. The way you do that is by engaging your core and focusing more on the “up” kick. 
  • Secondly, sort out your arms. Yes, your arms, not your legs! If you can get a friend to tape you when you swim, have a look at what your arms are doing. If your arm is pointing up when it’s forward, the current of the water actually contributes to that seesaw effect, moving your upper body upwards and causing your legs to sink.
  • To fix that, consider entering the water with your arm pointing down. This will lower your upper body and, if your core is tight and activated, the seesaw works in your favor by lifting up those legs. 
  • Finally, another issue with advanced sinky legs is a big kick that causes your quads to move your legs down and gets them sinking. To avoid that, open up your hip flexors and get your body accustomed to kicking lightly and well behind you.
  • A hip flexor stretch done often, maybe as you’re watching TV at night, really helps. Here’s how I do it:

A few other drills contribute to a good body position and nice, long and straight swim legs, especially in open water. We look at open water swimming tips – including sighting and how not to unfold completely when you’re trying to find your way! – in our “Panic Free Swimming in Open Water” guide.

Float Like a Log and Swim Faster and Smoother Without Sinky Legs

Performing the drills above, along with the tips we’ve covered in our section on breathing better while swimming, will make you faster, more relaxed and smoother in the water. There’s actually a nice connection between sinky legs, calm breathing and a relaxed demeanor in water because the calmer you are, the less you’ll be thrashing and causing your legs to sink. You can see more about that here

Sinky swim legs are not impossible to fix, and they’re not a beginner’s problem, either! To ace your next triathlon and maximize your energy levels while spending less time in the water, work on developing a strong core and add these drills into your swimming training routine to make sure you breathe like a dolphin and float like a log.

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Taren Gesell

"Triathlon Taren" Gesell is founder of MōTTIV and one of the world's top experts on helping adults become endurance athletes later in life. Best known for his YouTube channel and podcast Taren is the author of the Triathlon Foundations series of books and has been published featured in endurance publications around the world.