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Why Do I Sink When I Swim?

Discover the facts about floating and why you sink

One answer to the question 'why do I sink?' lays in your ability to relax in the water. Relaxation in the water is key to helping your body to remain afloat as you swim. If you are a beginner learning how to swim, it is useful to use some buoyancy aids to help get a feel for your own buoyancy. 

Not everyone is a natural floater, therefore getting a feel for how your body behaves in the water is vital to learning how to relax and how to help keep your body at or near the water surface as you swim.

How To Float

Myths, Tips and Tricks

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How To Float

Myths, Tips and Tricks

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The constant battle to keep your legs at the surface when all they want to do is go down.  It's all made worse when another swimmer glides effortlessly past you like a duck on a pond, without a care in the world! 

Click here for some simple exercises and tricks to help us learn how to float as we swim.

There is a very good reason why some of us sink and some of us float easily, and it's all down to our relative density.

Why Do I Sink? - The Solution

Key factors that are essential to learning how to float as you swim:

Learn To Relax - by learning how to submerge, breathe at the right time and stand up mid swim. These three key elements will erase tension as you learn how your body moves and behaves in the water. Click here to learn how to relax in water

Learn How To Glide - a gliding action through the water as you swim is key to relaxing and the momentum of a glide helps to remain at the water surface and prevent sinking. Click here to learn about gliding.

Efficient Swimming Technique - moving through the water smoothly and with minimum effort is essential for the natural sinker to stay afloat.  Correct swimming technique is a must for moving smoothly through the water.  Download The Swimming Strokes Book to learn smooth swimming technique.

'Relative Density' - The Real Reason We Sink

A stick floats and a rock sinks. The stick floats because its density is less, relative to the density of the water.  The rock sinks because its density is far greater, relative to the density of the water.  

In human terms, our fat is the stick and our muscles are the rock.  Muscles are generally more dense than water and cause us to sink.  Fat is less dense than water and therefore floats.  Those of us with a higher fat to muscle ratio will tend to float.  Yes that’s right, fat people float better than muscular people - generally speaking.  

(I’m using fat and muscle as examples to keep things simple, but it goes without saying our bones, organs, blood and all that stuff all contribute to our overall density.) 

Take a look at the figures in the diagram:

  • Freshwater has a density of 1g/cm
  • Saltwater has a density of 1.024g/cm3, therefore having a higher density

The average male has a density of 0.98g/cm3 and the average female 0.97g/cm3.  We can deduce therefore that most human beings will float to a certain degree, with a small amount of the body staying above the water surface.  Females float better than males and both males and females float better in saltwater than in freshwater.  Very few adults can float horizontally in the water, yet most children can hold a star float in the horizontal position.

Why do I sink?Relative density of a male and female in freshwater. Women float better than men!

It must be noted that a persons weight has little to do with their density.  Muscle is denser and therefore heavier than fat, making fatter people better floaters.

Other factors that effect floatation are:

  • The volume of air in the lungs
  • An individuals muscle to fat ratio
  • The shape of the individual and therefore the location of their centre of gravity

Almost every beginner learning how to swim will ask the question 'why do I sink when I swim?'.  It can be very frustrating, making your way through the water and having to fight with that sinking feeling at the same time. 

Simple exercises such as push and glides from the pool side, laying on your back with arms and legs wide or using some buoyancy aids are all great for learning to relax and learning how to float.

All of these exercises and loads more are available in 'The Complete Beginners Guide To Swimming' book. Click here for more information and to download it.

Even learning how to submerge will help you learn how to float. Yes, holding your breath and slowly submerging underwater will help all areas of swimming.  Learning that your body does not sink like a stone, but actually sinks very slowly, will in turn teach you to relax as you move through the water.

So next time you ask 'why do I sink?', remember that sinking is a characteristic of your body and your ability to float is dictated mostly by your body composition.   Based on the scientific fact that muscle sinks and fat floats (broadly speaking), you can see that fat people float well and lean muscular people tend to sink.  

In short, some people float and some people do not, but that does not mean you can't learn how to stay at the surface as you swim!

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