Wearing a mask
You should never strap a mask so tightly to your head that the frame distorts. Doing so will cause the mask to sit uncomfortably on your face, and it will be more likely to let water inside. The water pressure should be enough to maintain the watertight seal. The strap is simply meant to keep the mask in place on your head.
Clearing your mask
If you are diving deep in the ocean and your mask is dislodged and floods with water, you need know how to clear your mask.
A diving mask always includes a pocket that encloses the nose. This pocket gives you access to your nose so that you can pinch it to clear your ears, but it also allows you to eject water from a flooded mask.
To clear the water from your mask, hold the mask firmly against your head so that the skirt makes a good seal. Tilt your head back so that the water is all at the bottom of the mask and exhale gently through your nose. It’s a bit like blowing your nose without a handkerchief.
The air that is blown from your nose into the pocket formed by your mask pushes the water out through the bottom of the skirt where the mask is not held so firmly in place. The interior of your mask is no longer full of water but is now full of air.
You will find that small amounts of water will enter your mask from time to time when you are underwater. Holding the top rim of the mask frame and exhaling slightly through your nose is usually all it takes to keep your eyes and your mask dry.
Mask clearing is one of those skills that should be practised until you can do it as easily as blowing your nose. Once you have mastered this technique, you should be able to take your mask off underwater and replace it again or even change your mask for another one.
Clearing your mouthpiece If you periodically take your mouthpiece out of your mouth while submerged, you won’t drown but the interior of the regulator will flood with water.
As long as you exhale first when putting the mouthpiece back in, the water in the mouthpiece will be pushed with the exhaled air through the exhaust port of the regulator.
Sometimes, you may find that you have just breathed out when you dropped your regulator. What happens then?
All regulators have a purge control at the front. When this is pushed, it releases a strong yet progressive flow of air from the tank. This pushes out any water that may still be inside the second-stage of the regulator.
Essential advice
Whenever you do not have a regulator in your mouth, make sure your airway is open by exhaling some air gently from your mouth. It is also a good idea to do this when ascending to allow some of the air that your body has absorbed underwater (and that is slowly expanding on the ascent) to escape through your mouth.