Your mask is probably the most critical fit item of your entire dive gear collection. A poorly chosen mask will not consistently provide a clean dry air space in which your eyes can focus. A leaking mask that you need to repeatedly clear will add to task loading. As you start to do things such as carry a light on a night dive, manage a dive flag or control the air in a drysuit you do not need to be fussing with your mask. In addition to not leaking the lenses must remain clear of foggy condensation. Most serious dive incidents occur when a series of things go wrong. Don't let you mask be part of an incident history.

Modern dive masks are generally made in a goggle format where the eyes are in a major space and the nose is in a connected compartment. The two spaces are connected so that when you exhale through your nose air will fill the eye space and displace water thus clearing the mask. The nose space is a thin pliable form that allows you to pinch your nose when performing the Valsalva maneuver. The skirt may be a clear silicone or a black silicone. The clear will admit more light sometimes relieving a sense of claustrophobia. The clear material will usually yellow over time though not to any detriment. A black skirt will block out extraneous light and they are preferred by photographers and enjoyed by many who prefer not to have stray light bouncing around.

In addition to the primary lenses many masks have additional lenses to add to your peripheral vision. You may not clearly see anything through these but they are sometimes enough to confirm the presence of a buddy to your side without turning your neck. Some masks have lenses that extend downward and lay in close to your cheeks. These can help you see the gear on your chest and can be convenient. Don't let this be a crutch. You need to know your gear by touch in any case.

Be sure to get a mask with a nice broad strap. I have seen some with very narrow bands of silicone and they look scary. Be sure to get a spare strap for your save-a-dive kit.

The big trick is to confirm that it will seal comfortably to your face. This is best done with your regulator mouthpiece in your mouth, a snorkel is better than nothing. The reason for the mouthpiece is that it will modify the contour of your face. Take a mask of interest and with the straps out of the way press it lightly to your face as you hold your breath. An exceptional fit will grab like a suction cup. The next level is to inhale lightly as you put the mask to your face, will it hang on easily? Don't inhale forcibly, that won't prove anything. As you try different masks the differences will become apparent. If you have not tried litterally dozens of masks don't say,"I tried everything".

Vaseline is said to help with sealing over a mustache. Laugh lines can be a challenge.

As you get your mask in the water for a real test be certain not to over tighten the strap. If too tight the skirt will be splayed out and it won't function correctly. More mask problems have been solved by loosening the fit than by tightening.