Underwater visibility without a mask is blurry. This is due to the fact that water gives us an excessive case of myopia (about 18 degrees). This can be corrected with the placement of an air layer between our eyes and the water. This is achieved with the use of a mask.

There are many mask models: crystal masks (single-optical), crystal masks (bi-optical), big, small, in various colors, lower or larger inner volume models etc. For u/w hunting one must use a comfortable mask in order to relax easily and stay focused on their dive. It must also offer a wide optical field, which will result in less stress of the neck, due to not having to make many or wide movements of the head in order to observe the surrounding environment. Finally, the mask must have a low inner volume, in order not to have to use air excessively for its equalization.

Subsequent to its use, the mask must be very well washed with fresh water and placed inside its case, in a shaded room, without any weight placed over it.