Sink while swimming

Why do we sink while swimming?

Why do we sink while swimming?

Why do we sink while swimming? I’ve had this question about a million times over my years of swimming instruction and because of this, I’ve had to develop a sufficient answer for all of my students to truly understand it. If you are struggling to stay a float while you are swimming, it can be very beneficial to your swimming abilities if you understand why it is you are sinking. What are the reasons people sink? What makes really good swimmers sit on the top of the water? I’m going to give you my best answer to this now.


So, if you are like me and you skipped a few of your physics lessons, here’s the crash course:

“Archimedes Principle: A body in water is buoyed or pushed upwards up by a force equal to the weight of the water it displaces” (Red Cross – AWSI Manual, 2005)

This really just means that if something or someone is going to float, they need to displace a volume of water that is equal to their weight in the water. We need to use our bodies to DISPLACE water if we don’t want to sink while swimming.

This means being aware of things like:

  • Holding your head out of the water
  • Looking forward in the pool
  • Keeping your ears out of the water
  • Not tilting your chest towards the bottom of the pool while you are doing a front float
  • Tensing up our muscles (which is making us more dense and more likely to sink)

So what can make a BIG difference for you is to start noticing if there are other body parts that you can just relax and “let droop” into the pool a little more. Or even consciously looking for tension in your body and letting it go can be key!

So that is buoyancy. What other factors are there that could be affecting your ability to swim? What could be making you sink while swimming? Here, I’ll name a few:

  1. Body Type
  2. Lung Capacity
  3. Body Position
  4. Age

Body Type:

What is your body type? The human body is made up of over 60% water and along with that, we have other “stuff” that can either aid or hamper our ability to float. Some people sink in the water worse than other people do. And this is the very reason why!

Muscle vs Fat:

Now, before I say this, don’t start rationalizing that “oh, this is why I suck at swimming. I just don’t have the right body composition.” Because that’s a load of crap. Anyone can learn to swim, no matter the body type or disability hampering them.

Muscle or muscular people have a tendency to sink. Fat or people with a bit more fluffiness have a tendency to float easier. There are a whole bunch of reasons for this that I could even start to explain using a bit of chemistry, but that isn’t going to be of much help for you. Just know that fat is a molecule that is “less dense” than water and will therefore allow you to float. Muscle is a molecule that is much more dense with water and will therefore cause you to sink.

These can affect your ability in the water, but they don’t determine whether you will be successful or not. The human body is still made up of 60% water. Over half of your body weight will still easily float on the water surface. There are a lot of fruits and vegetables out there that will float on their own and they are made up of just 80% water. AND they don’t have any propulsion helping them. You can do this.

Lung Capacity:

Lung capacity determines if I will sink while swimming huh?

Yes it does. And from everything we have talked about before, it makes sense. You are filling your body with more air. Why wouldn’t you float better? When you have a big ball of air in your chest, damn rights it’s going to keep you a float longer!

Now, this is a very interesting one too, because we can affect it to a certain degree! We can modify how we swim and our lifestyles to try and improve this. There are ways of increasing your lung capacity, you just have to commit to them. It should be easy if improving your swimming is something you really want to do!

  • People more physically active have a larger lung capacity
  • People who smoke have a smaller lung capacity
  • People who are at the extreme end of age (children and seniors) have a smaller lung capacity
  • Holding more oxygen in your lungs/ taking a deeper breath when you swim
  • And many others

So this may be as simple as waiting until you’re a little bit older or you may be having to make a bit lifestyle change such as stopping smoking. Just know that lung capacity does have an effect on your swimming and that it can be improved!

Body Position:

Will you float if you are standing up in the water? No.

Will you float if you are lying face down in the water? Yes.

There is a simple reason to this. We are spreading out our mass. We are allowing the buoyant forces to keep us a float more easily. We have moved our centre of gravity to a place that will allow us to float, rather than sink while swimming.

This is an easy thing to understand on the surface, and it has one simple application for you to try out. If you are sinking, you are most definitely putting your centre of gravity in a place that is not aiding in your ability to stay a float.

You are not floating because you are holding your head out of the water or because you are not “tilting” your chest down towards the bottom of the pool. You are not putting your centre of gravity in a place that is aiding your buoyancy. You are causing yourself to sink while swimming by setting up a poor body position.

So change it. Find that comfortable body position. That position that you feel balanced in. Looking at the bottom of the pool. With relaxed body language. It’s going to make a huge difference for you. I promise.


This is a quick one, and it is tied in with body type, but it is worth mentioning. With age certain factors about your body composition, body language, and physical fitness change.

When you look at a lot of small children, they are very scrawny. This makes for a real sinker.

When you look at a lot of old folks, they favour a shoulder a little bit because it aches for them. This tension makes it harder to float.

When you are younger, your lung capacity is less. You therefore have a harder time floating (air is really light y’all!).

So just be aware that age can affect a lot of the previously mentioned factors!

I hope that this has been an educational week for you guys. Hit me up in the comments if you want to learn more! Cheers till next week!

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