A MASK IS OUR “WINDOW TO THE UNDERWATER WORLD”, they say – an essential item with a simple job to do. Selecting a model that suits your needs can be daunting, however, because there are probably more variants in mask design than in any other dive-kit item.
The overriding factor to consider is fit. Forget about style and colour initially and concentrate on finding a model that fits your face shape and size.
A mask that doesn’t fit is about as useful as a button on a sock, and an ill-fitting one will leak and steam up, making your dives a hateful experience.
You need to try a mask on in the shop and get expert advice rather than get the same mask as your buddy or search blindly online. Here is everything you needed to know but were afraid to ask:

LENSES
There are two basic lens variants, twin or single. Single-lens masks have no frame construction between the eyes so can give a better view, but it’s not possible to replace them with prescriptive versions, as you can with twin-lens models.
There are also masks with extra side lenses to boost peripheral vision, and these tend to be bigger in size and profile.
Glass specification, lens shape and special coating options also need consideration. The glass must be tempered, and this is usually marked on the lens as a “T” or the word “Tempered”.
Standard glass can shatter into razor-edged shards but tempered glass is treated to increase its strength. When it shatters it forms larger, granulated pieces with rounder edges, reducing risk of injury.
Standard tempered glass contains impurities including iron. This gives the glass a slightly green hue and can reduce light transmission.
Removing the iron content allows more light to pass through, giving a clearer view; such lenses are normally referred to as “Ultra Clear” or “St Gobain” glass, but are more expensive.
You can choose from teardrop, square and rounded lenses. An elongated reversed teardrop is very popular in modern masks and helps you see items in your chest and waist areas, such as instrument consoles. A wider rectangular or rounded shape is better for lateral vision.
You can also obtain specially coated lenses for certain models. These may be made from high-grade optical glass with the additional coatings further reducing the amount of light reflected away from the eyes.

FRAMES
Framed masks form a rigid structure with skirt, strap-buckles and lenses attached to it. The frame offers infinite colour options and can be dismantled for cleaning, repair or to fit prescription lenses. It can cause discomfort if, like me, you have an oversized nose that can come into contact with the base.
The alternative, frameless masks, have the lenses moulded directly into the silicon skirt with the buckle mount forming part of the skirt. This creates a very streamlined profile that can be folded in on itself for packing, or tucking into a BC pocket as a spare.
Frameless mask lenses can’t be replaced if they break or a prescriptive version is required. They are usually single-lens designs, as the glass itself provides the mask’s rigidity.
skirts
The skirt is there to keep water out and the air in. It also encompasses the nose and needs to be soft enough to allow for easy nose-pinching when equalising your air spaces, so it must be able to mould itself around your features.
To this end soft silicon is the best material, with manufacturers vying to find innovative ways of maximising the sealing properties through differing grades or thicknesses of super-soft silicon, or even building a secondary seal into the skirt.
Some skirts use a silicon additive to reduce the damaging effects of UV light and prolong the mask’s life.
You can choose a clear or opaque (usually black) skirt. The former will let in more light, so the wearing experience is brighter and less claustrophobic.
Opaque skirts are preferred by underwater photographers, who don’t want stray light causing them to see their eyes reflected in the lenses when looking through camera viewfinders.

STRAPS & BUCKLES
A silicon head-strap holds the mask in position and maintaining the seal between skirt and face. Everyone is different so this needs to be adjustable, and to have a degree of stretch to avoid restricting movement or affecting the integrity of the seal.
Various designs are available, either supplied with the mask or as an after-market replacement. Silicon straps can be annoying, especially for divers with long hair, because it can get tangled in the strap and making removing the mask painful.
An alternative is a neoprene “slapstrap” with adjustable webbing or Velcro fastenings (above).
The straps are connected to the mask by a buckle attached to either the frame or skirt, with some versions swivelling to add flexibility and allow the strap to be positioned correctly just above the ears.
Buckles are usually fitted with a spring-loaded locking mechanism to keep the strap in position and stop it loosening during the dive.

VOLUME
The internal volume of a mask is the confined airspace created when it’s sealed to the face. The larger this is, the more it’s subject to compression on descent, needing more air and effort to equalise.
Freedivers see very low internal volume as a crucial factor, as they have to use air held in their lungs to equalise and reduce their breath-hold time.
A low-volume mask generally places the lenses closer to the eyes and increases the field of view, and is much easier to purge.

FIELD OF VIEW (FOV)
The amount of the underwater world you can see through a mask is often referred to as the field of view, or FOV, and such factors as lens shape, size, glass material, internal volume and rake all come into play in determining this.
The rake is the angle at which the frame or lens sits in relation to the face. By bringing the bottom of the mask closer to the diver’s cheeks the frame becomes less visible and allows for easier viewing of instruments.
Reversed teardrop-shaped lenses also aid in this department. Wide single-lens masks generally offer the best peripheral vision.
Some divers actually prefer a narrower field of view, especially when hunting for macro subjects. Their focus can be concentrated on a smaller area, making tiny critters easier to find.
Reef nuts like me prefer as wide an angle of view as possible so that the whole scene can be enjoyed at a glance. What matters to everyone is an uninterrupted view downwards, so critical information from instruments can be easily seen.

FOG PREVENTION
When masks are made the silicon skirts are injection-moulded, and to stop the silicon sticking to the inside surfaces of the moulds an oily chemical release agent is applied.
This ends up coating the skirt and strap and invariably ends up coating the lenses. This causes the glass to become hydrophobic, which prevents water from adhering.
A warm wet face and a cooler water environment will make the glass steam up. What’s needed is a fine coating of water that’s transparent and won’t run off or form droplets, thereby stopping this fog from forming in the first place.
A detergent-based liquid will break the surface tension of the water and allow the glass to stay coated, but the release agent needs to be removed first. The best method is to scrub the inside surfaces with toothpaste. This needs to be done to all new masks and repeated several times before you can enjoy fog-free diving.
A worrying modern trend is to try to burn off the release agent with a cigarette lighter. This is bad news. The locally intense heat retempers the glass in small areas, weakening it immensely, so don’t do it!
After cleaning the lenses with toothpaste a propriety liquid mask de-fogging agent such as Sea Drops can be applied just before a dive to break the surface tension. Johnsons Baby Shampoo is cheap, works a treat and won’t bring tears to your eyes.
TUSA produces a stick-on plastic film for certain mask models and I’m informed that this stops fogging completely.

THE TESTS
I asked mask manufacturers for samples covering the widest spectrum of design and genre in the marketplace. My choice process proved what a confusing task mask selection could be. I settled on the 22 models showcased below, but could easily have had 50 or 60.
I devised a method of measuring the field of view to compare differing styles and models (below).
I set up a matrix with numbers (not measured distance) set on two axes, one vertical and one horizontal, to record how many numbers I could view through each mask.
For consistency I used a measuring stick from my chin to the matrix, so my position remained the same throughout. The results need to be read in context with this test feature alone and are for comparison purposes only.

IN THE POOL
Sue Coffey and Martin Weddell of Berkshire-based Divecrew (www.divecrew.co.uk) generously offered me their pool time and two of their crew to take the masks under water. Jackie Austerbury and Andy Harfield are divers with differing facial shapes and sizes, and inevitably they found some models an extremely poor fit while others were perfect.
Divemaster Jackie’s long hair was a constant problem, getting caught in the straps and buckles when donning and doffing the masks. She uses a neoprene strap on her own mask.
I spent a few days scrubbing the 22 masks with toothpaste, a Herculean effort that left me without fingerprints. Our results proved that this essential task needs to be performed more than once, although with a bit of baby shampoo and perseverance we were able to enjoy fog-free diving.
The masks are arranged in ascending price order, and all are unisex unless otherwise stated. The field of view is shown on the right – which suits you?
SubGear Mini Vu     £23
The Mini Vu is a twin-lens framed model designed to fit teenage or female divers with smaller faces. The inverted-teardrop lenses are made from tempered glass set in a rigid frame. The skirt uses quite a firm silicon and, like all the models here, has a twin sealing flange to increase surface area on the inside. Tightest FOV of all the masks tested. Buckles attach directly to the skirt and have a quick-release swivel and lift-to-release mechanism to adjust or lock the strap. The Mini Vu has a clear skirt and two colour options.  
IST Chameleon      £36
This framed twin-lens mask has a hypoallergenic liquid-injected silicon skirt, which IST says has been designed to avoid allergic reactions and is built to fit a wide range of facial profiles. The tempered lenses are an inverted teardrop shape and provide good all-round vision; the frame is raked to enhance the lower vertical view. The Chameleon is available with a clear silicon skirt and four frame colour options. Snap-on ornamental frame pieces are included to add a touch of individuality to each mask.  
SubGear Steel Comp      £37
This twin-lens frameless mask for freedivers has a small profile and very low volume, putting the Ultra Clear lenses closer to the eyes and increasing the field of view. The soft-silicon skirt compresses as the ambient pressure increases, negating the need to constantly equalise. As the skirt compresses the mask bends and distorts the lenses, so it is unsuitable for scuba-divers. The buckles have a quick-release swivel and are attached directly to the skirt. The Steel Comp comes in either all-clear, all-white or all-black.  
IST Chameleon Ultra Clear      £40
This twin-lens frameless mask for freedivers has a small profile and very low volume, putting the Ultra Clear lenses closer to the eyes and increasing the field of view. The soft-silicon skirt compresses as the ambient pressure increases, negating the need to constantly equalise. As the skirt compresses the mask bends and distorts the lenses, so it is unsuitable for scuba-divers. The buckles have a quick-release swivel and are attached directly to the skirt. The Steel Comp comes in either all-clear, all-white or all-black.  
Scubapro Solo      £40
The Solo is a frameless single-lens mask with a large rounded shape. The tempered lens is quite wide and is moulded directly into the silicon skirt with a coloured accent around the lens edge. The mask is slightly raked towards the bottom to enhance the downward view and is held close to the eyes, reducing internal volume. The soft silicon strap has the twin-button press-to-release buckles fitted directly to it. The strap has a large 3D pad at the back. The Solo has black or clear skirts and three colour options.  
Mares X-VU LiquidSkin Sunrise      £49
This is a twin-lens, tempered-glass, framed design with a LiquidSkin skirt comprising two grades of silicon. One is coloured and firm for support, the other clear, soft and elastic for a better seal. The softer silicon is also injection-moulded in the nose-pocket, with moulded ridges to stop it collapsing. The bi-silicon mask-strap has a 3D anatomical back to hug the head, and the buckles fit directly to the skirt. The Sunrise comes with a black and grey or clear and white skirt and five more colour frame options. Corrective lenses are available.  
Aqua Lung Look HD      £50
The rugged techno-polymer frame on this twin-lens mask is reinforced with inorganic fibres and a stainless-steel torsion bar to stop it flexing and placing the lenses out of alignment, so preventing distortion. The mask has a soft silicon skirt with bands of differing textures for a better seal. Cardanic buckles that swivel up, down, in and out are fitted to the frame. The 4mm-thick lenses are made from standard tempered glass. The mask is available in all-black or with a clear skirt with black and white frame.  
Scubapro Spectra Mini      £50
The rugged techno-polymer frame on this twin-lens mask is reinforced with inorganic fibres and a stainless-steel torsion bar to stop it flexing and placing the lenses out of alignment, so preventing distortion. The mask has a soft silicon skirt with bands of differing textures for a better seal. Cardanic buckles that swivel up, down, in and out are fitted to the frame. The 4mm-thick lenses are made from standard tempered glass. The mask is available in all-black or with a clear skirt with black and white frame.  
Cressi Nano      £55
The rugged techno-polymer frame on this twin-lens mask is reinforced with inorganic fibres and a stainless-steel torsion bar to stop it flexing and placing the lenses out of alignment, so preventing distortion. The mask has a soft silicon skirt with bands of differing textures for a better seal. Cardanic buckles that swivel up, down, in and out are fitted to the frame. The 4mm-thick lenses are made from standard tempered glass. The mask is available in all-black or with a clear skirt with black and white frame.  
Oceanic Cyanea      £55
Oceanic says its design team has focused on addressing common mask problems, such as restricted field of vision, discomfort and where to stick your snorkel. The lenses use Ultra Clear optical glass and are shaped and raked to gain the best FOV. The skirt is made from liquid silicon with a ridged and feathered edge to provide crease resistance. The strap is an elasticated ski-goggle design with a built-in loop to retain the snorkel. The Cyanea comes with clear or black skirts with seven strap and frame colour combinations.  
Aqua Lung Linea      £56
This single-lens mask is part of Aqua Lung’s women’s range. The tempered lens, skirt and sleek frame are moulded as one, so the lens can be positioned very close to the eyes, resulting in excellent field of vision as well as very low volume. The mask has a large, soft silicon skirt with bands of differing textures for a better seal. Buckles are Aqua Lung’s full-swivel Cardanic Joint versions fitted to the frame for fine adjustments. Guards are built in to prevent hair tangles. The four-colour Linea comes with clear or black skirts.  
Mares X-Vision LiquidSkin      £57
Inventively shaped twin tempered lenses are set into a frame attached to a LiquidSkin skirt, with two grades of silicon moulded together for firmness and soft elasticity. Small horizontal ribs add stiffness around the nose-pocket to prevent the frame collapsing onto the diver’s nose. Squeeze-to-adjust buckles are attached directly to the skirt, and the strap has a large bi-silicon head-pad. The mask is available with twin coloured silicon skirts in black, white or clear with a total of eight optional colour combinations.  
Scubapro Synergy 2      £57
Just released, this framed single-lens mask has a unique skirt design. Though it’s based on Scubapro’s Trufit technology, a secondary silicon outer skin sits over the thinner inner skirt to add support. Both outer skin and inner skirt have moulded ribs throughout to add rigidity. The single Ultra Clear glass lens sits in a slightly raked frame. Buckles attach to the inner skirt, with twin pinch-buttons to adjust the strap, which has an anatomical head-piece at the rear. This mask has clear or black skirts and four colour options.  
Scubapro Synergy Twin      £60
This two-lens framed mask also uses TruFit skirt technology. The inverted-teardrop Ultra Clear optical glass lenses have a slight rake towards the base. The skirt is made from extremely soft silicon that’s thicker and firmer near the mask frame for support and rigidity, while the edge is thinner, giving a softer feel and a better seal, and has a ribbing pattern to stop it collapsing under pressure. The strap-buckles are attached to the skirt. Choose from black or clear skirts with five colour combos plus optional tinted, anti-reflective lenses.  
IST Gauge      £60
This four-lens framed design is for divers who need optical assistance to read or focus at close distances. The tempered lenses are clear at the top with +1.75 dioptre magnifying lenses set at a 50° angle at the bottom to facilitate reading of gauges, compasses, computers and camera screens. The skirt is moulded from liquid silicon and has the strap-buckles attached. The Gauge comes with a clear skirt and two colour frame options or a black skirt with a black frame. Not surprisingly, this is a very popular mask.  
TUSA Ceos      £61.50
This twin-lens framed mask from Tabata USA (TUSA) employs the same technology as on its single-lens sibling, the Freedom Elite. The skirt employs round-edged, varied-thickness soft silicon with dimples and ridges to enhance comfort and fit. The Ceos comes with a black skirt and seven frame colour options or clear skirt with nine frame colours. The test mask had tempered glass but a Pro version has CrystalView lenses with an anti-reflective coating to block out 100% of UV light. Prescriptive lenses are available.  
Hollis M1      £64
The M1 is a single-lens frameless mask with a rounded design. The soft silicon skirt is moulded in one piece around the lens with a matt exterior finish and a gloss interior, and a larger nose-pocket than other masks here would suit those with bigger noses. The lens is raked towards the cheeks to enhance downward vision, which, with the wide lens profile, gives a great all-round field of view. The lens uses optical-quality St Gobain glass. Strap-buckles are attached directly to the skirt. The MI comes in all-black only.  
TUSA Freedom Elite      £64
This single-lens framed mask with tempered glass has the Freedom style of round-edged skirt with dimpled surface and varying silicon thickness with stability ridges. The buckle is fitted to the frame and swivels in and out as well as up and down. The silicon strap has a 3D split that fits snugly to the contours of the head. The mask is available with a black skirt and three colour frame options, or a clear skirt with a further six colour options.  
Cressi Big Eyes Evolution Crystal      £65
This twin-lens framed design has inverted teardrop-shaped tempered lenses. Cressi was one of the first makers to realise the value of a raked angle to enhance FOV, and has patented the optimal angle used in its masks. The crystal silicon for the skirt was developed for Cressi and is very soft, transparent and treated to prevent discolouration. The silver strap is made from a different grade of silicon, and the buckles are fitted to the frame. The Crystal version has five colour options and will accept prescriptive lenses.  
Atomic Aquatics Frameless 2      £80
This unisex mask has no frame, and the large single lens is moulded into the silicon skirt. The skirt is made of two grades of silicon, the main body using a stiffer grade, and the area around the seal uses a very soft pliable grade to ensure a good seal. The lens is made from Ultra Clear glass and is held close to the eyes, giving a very wide FOV. A slight rake towards the bottom of the mask enhances the view of chest and waist areas. The strap is a soft silicon split-pad design. Available in either all-clear or all-black in three sizes.  
AquaViz UTS Pro Core      £55 + Inzerts from £45
The UTS is part of the range of Core masks suitable for use with Sportviz Inzerts. The mask is a framed model with a tempered single lens. Its large profile allows for fitting an Inzert ophthalmic frame with prescription lenses and the mounting rail. Inzerts come in four standard bifocal dioptres as stock items, and custom Inzert lenses are also available. The positioning of the Inzert in the mask is fixed but puts it at the same distance from your eyes as a normal pair of spectacles. Tight FOV. The mask comes in all-black only.  
Atomic Aquatics SubFrame ARC      £110
The SubFrame is a framed twin-lens mask with a twist – it has an internal main frame that’s bonded directly to the silicon skirt with a secondary lens retainer locked in place with a stainless steel bridge. This results in a low-volume profile but enables the lenses to be removed and replaced with prescriptive versions. Fitted as standard with Ultra Clear glass lenses, the model on test had the optional anti-reflection coating (ARC). The SubFrame comes with clear or black skirts with 12 colour options and combinations.  

CONTACTS
Aqua Lung, www.aqualung.com/uk
AquaViz, www.sportviz.co.uk
Atomic, www.atomicaquatics.com
Cressi, www.cressi.co.uk
Hollis, www.hollisuk.com
Mares, www.mares.com
Oceanic, www.oceanicuk.com
Scubapro, www.scubapro.com
Sea & Sea, www.sea-sea.com
Sub-Gear, www.subgear.de
TUSA, www.tusa.com