When it comes to diving, vision is crucial. But underwater, the human eye struggles to see clearly and has a limited field of vision. That's where a good dive mask comes in.
A dive mask creates a pocket of air around the eyes and nose, simulating the eye's natural environment and allowing for clear vision underwater. But with so many types of masks available, how do you choose the right one? Here's what you need to know.
Why do you need a diving mask?
The human eye is not designed to work well when immersed in water. Vision is blurry and the field of vision limited. Because the eye is designed to see through air, a lighter and less dense medium than water, a surrounding pocket of air is required in order to simulate the eye’s natural environment.
First attempts to overcome the problem of distorted underwater vision produced a device similar to the modern swimming goggle; a design unsuited to diving because water pressure at depth squeezes them against the face, causing discomfort and the risk of injury to the eyes and surrounding tissues.
A larger, more flexible enclosure was necessary. This was achieved with the introduction of a single lens mask surrounding both the eyes and the nose, a practical design that allows the wearer to exhale into the mask and bring its internal pressure into balance with the external water pressure.
Choosing a Mask Style
Single Lens masks are generally high volume and the plate of glass-lens sits further away from your face. This mask is generally chosen for those who have a larger brow or nose and require more space to allow the mask to not press against the nose or brow.
As this mask will have a higher volume it requires more air to equalise or to clear if flooded. Having a larger single lens however has the advantage of giving a large field of vision if well designed and is very popular for models underwater as it allows the photographer to capture the models face.
2 lens masks are the most common option for Freedivers and they are generally low volume and have a nose bridge that sits between the eyes holding the lens. This allows the glass to be located closer to your face with a smaller skirt. This allows you to equalise the airspace easier at depth along with clearing any water that may have entered.
Could be made any colour most common is clear or black and other solid colours - Silicon is the most common material used in mask skirts and straps. Because Freedivers spend considerable time on the surface, their preference is for black silicone that prevents confusing light glare from penetrating the sides of the skirt. Other advantages of silicone is that it is very resistant to the ozone and UV light compared with Rubber or Silitex. You will also find that silicone does not have an odour or taste and is hypoallergenic.
Was once the most common material used for masks prior to silicone technologies becoming our best option. The rubber materials were normally black however could also be made other solid colours like blues and yellows.
The disadvantage with rubber was it did not have a good resistance to UV light, heat or the ozone so would crack and break down quickly if not cared for. Rubber requires storage in a cool location, should be powdered with talc to help prolong life and kept in a sealed airtight container. Rubber also has the disadvantage of having a distinct odour and some people can have allergies to rubber or latex.
Often used as a cheaper material for mask skirt manufacturing is a mixture of silicone and PVC and does not have the same softness, UV stability or Ozone resistance as high grade silicone.
Silitex/PVC masks are often purchased as a mistake as the name Silitex look very similar to the name silicone, however they are far apart in quality with Silitex also having a plastic like odour and often becoming deformed in shape when left in sunshine.
The important features to look for when choosing a mask are:
The lens should be made of tempered or safety glass. The lens faceplate in a new mask is usually protected by an oily film. This coating must be removed - using a mild cleanser or commercial mask scrub- before applying a commercial anti-fog solution.
Be aware some mask’s may have a special coatings and be pre-treated with a longer-lasting antifog so it is worth checking with your dive store. Masks may also have tints, UV filters and factory coatings, so always follow the directions from the manufacturer on how to prepare your mask.
The mounting band for the lens should be non-corrosive— moulded plastic or composite.
The strap should adjust, and lock in place, easily. It should also be either split at the back of the head, or wide enough to fit comfortably and securely; a narrow single band will easily slip up and down.
Nose - or finger - pockets allow the Freediver to overcome the effects of depth and equalise pressure in the ears and sinuses during descent.
Selecting a mask with a suitable nose pocket is an important step always make sure the pocket can accommodate your nose without causing any rubbing or applying any pressure on your nose. Practice equalising or pinching the nose pocket making sure it is easy to pinch the nose.
The Freediver requiring vision correction has several options. The nearsighted Freediver may choose off-the-shelf corrective optical lenses – measured in diopters – offered by some manufacturers as a replacement for the standard lenses in their particular mask models.
Vision can also be corrected by integrating prescription lenses into a dive mask. The prescription lenses are ground and then affixed directly to the inside of the mask lenses by a qualified optical laboratory. It is also possible to use contact lenses.
All vision correction decisions should be made with the consent and approval of your optometrist, who should coordinate with the dive retailer.
Fitting the Mask
Fit and comfort are paramount. Masks, like facial contours, differ. The objective in finding a mask that fits is to match the mask skirt to the face. The soft material of the skirt should fit evenly and comfortably against and around the face, without pinching.
The skirt should form a seal with the face. Many masks incorporate a double seal for greater comfort and to further reinforce the skirt’s sealing ability. Silicone masks form the best seal. To check the fit of a mask, tilt the head back and, before strapping it to the head, lay the mask on the face.
The force of gravity alone should keep a good fitting mask in place. Run a finger around the mask skirt to ensure that the entire sealing edge touches the face. Then inhale gently through the nose to hold the mask against the face, tilt your head forward and look straight ahead.
The mask should remain in place with only a gentle inhalation through from your nose. Test several different models to find the one that fits best with the least amount of inhalation whilst being the most comfortable. We call this challenging the mask seal, when we try to fit and find the mask that fits with the least possible nose inhalation effort as possible to hold it in place.
Remember as soon as you exhale out of your nose it will pressurise the mask and no longer vacuum to your face during this test. If you need any help selecting a mask drop into our dive store.