Mask clearing is essential for scuba divers and is one of the first skills a diver is taught. No matter how good a fit your mask is, a leak in your mask can always occur, so it’s important to be able to clear it quickly and effectively. A mask might also need to be cleared when it fogs up. And of course, there’s always the chance that your mask may come off in the water, and you need to put it back on. Luckily, mask clearing is an easy skill to develop.
Stay calm and remember to breathe. For new divers, it can be intimidating to be many feet below the surface of the water and find that your mask is quickly filling with water. It is most important to stay calm and keep breathing. You still have your regulator for oxygen so you're not in any danger.
Press the top of your mask firmly against your forehead. This is an important step. Forgetting to do this can cause more water to enter your mask.
While still pressing the top of your mask against your forehead, tilt your head up and look up and exhale out your nose. Make sure that you start to exhale before you begin to look up to prevent water getting into your nose.
Repeat the process until your mask is fully cleared. This can take 2 to 3 times to complete.
If your mask has a purge valve, you need to do things a little differently. Hold the mask pressed against your entire face and look down. The purge valve should now be the lowest point in your mask. Take a breath and exhale out your nose, causing the air to force the water in your mask out through the purge valve.