For a full explanation about our body underwater when scuba diving, you will need to Open Water Scuba Dive Course

Scuba diving is a physical activity that should be undertaken by people in good health.

It is wise to get a check up by a qualified physician prior to participating in scuba activities, and never dive when sick.

There are many air spaces inside of our bodies, but only some of them are directly affected when we scuba dive.

It is good to know about these air spaces and what happens when we go into the underwater environment. Can you guess what they are..?


.First of all let’s think about how to keep our lungs healthy while scuba diving.

The key rule in scuba diving is to always breathe, never hold your breath.

However, the easiest way to understand it at a fundamental level is first to imagine a full balloon of air at the surface of the water.

If you took the balloon beneath the surface, the air inside the balloon would be compressed, getting smaller and smaller the deeper you go.

If you then brought the same balloon back up towards the surface the air inside it would expand, getting bigger and bigger until it’s at full capacity again when back at the top. Does that make sense?

Now try to imagine what would happen if you were underwater scuba diving, you took a deep breath, filled your lungs full of air, held your breath and started to go up.

What do you think would happen? …Just like in the balloon the air inside your lungs would expand – if we hold our breath and the air in our lungs expands too much for the space then we could give ourselves an injury.

This is very easy to avoid with the key rule in scuba diving – always breathe, never hold your breath. Easy!

It’s something you do all day, every day so you are pretty good at doing it. You wouldn’t walk down the street and stop breathing …so don’t stop underwater.

Even if the regulator is out of your mouth, teach yourself to exhale a steady stream of bubbles so that you are keeping your airways open – see section on ‘What to do during the scuba dive‘.

If you take an introductory scuba class or participate in a fun resort dive, your dive leader will explain this to you so that it becomes clear.

Don’t worry if you can’t quite understand it here.


When scuba diving, we need to know how to equalise the pressure inside our ears in order to go underwater comfortably.

Similar to our lungs, we have a little air space inside our ears that is compressed when we go underwater.

Have you ever felt the change in pressure on your ears when you go in an aeroplane? It’s exactly the same feeling when we scuba dive!

The way we equalise – or ‘pop’ – our ears while we dive is really easy: simply pinch your nose closed with your thumb and index finger and try to gently exhale through a closed nose.

You should feel a slight ‘pop’ in both ears. (The nose pocket is built into the mask so that you can do this with your mask still in place).

Remember to be gentle with your ears, equalising should never be done forcefully.

You should gently equalise – or ‘pop’ – your ears at the surface and continually as you dive deeper.

The great thing is your ears will tell you when they want to be equalised.

So you might go underwater a little bit and feel a slight change in pressure on your ears, ‘pop’ and you’ll be able to go deeper – slight change again, ‘pop’ and you’ll be able to go deeper – change again, ‘pop’ and you’ll be able to go deeper.

Continue to equalise your ears every time that you feel that slight change on your ears throughout your dive.

If you don’t equalise your ears, you won’t be able to go underwater comfortably.

If you are having problems equalising your ears, there are lots of things you can do. You can try things like wiggling your jaw or swallowing – the same things that help your ears to pop on an aeroplane. If you are having a problem popping your ears don’t keep going deeper. If you keep going deeper without popping your ears the pressure will get greater and eventually you could hurt your ears. Your ears should never, ever hurt.

Instead, if you are having problems popping your ears, ascend very slightly in the water to where your ears are comfortable and try gently equalising again.

It is very important if you are having problems equalising your ears that you tell your Scuba Instructor straight away.

They will assist you to come up slightly to where your ears are comfortable.


Another air space that needs a mention is our sinuses.

Most divers don’t feel this one at all, but do you know how it feels when you’ve got a cold and you can feel all the congestion around your nose, your cheeks and your forehead?

Well unfortunately if we feel any kind of pressure around our sinuses when we start to dive, there is little we can do about it. It is best not to scuba dive until your sinuses are clear.

Just remember, never dive when you’re sick.




scuba dive mask

The last air space isn’t inside of our body, it’s inside of our mask. If you feel the air inside of your mask getting smaller, or your mask getting squashed against your face as you descend under the water,

what do you think you should do? …Simple – breathe out of your nose a little bit!

Just add a bit more air.

Most scuba divers do this subconsciously anyway.