Mares Seal Skin Cold Water Semi-Dry

Mares Seal Skin Cold Water Semi-Dry

0818 tests seal skin1

Appeared in DIVER August 2018

THE MARES SEAL SKIN is very much a coldwater wetsuit. It’s designed to attract those who, for whatever reason, prefer to dive wet rather than dry. Such divers include those who can’t afford a drysuit, and clubs and schools that prefer the simplicity of teaching students in wetsuits.

Because coldwater wetsuits can also be used for temperate conditions, this one might also appeal to professional divemasters working in “warmwater” locations that begin to feel chilly halfway through the working week when wearing less-efficient suits.

The Seal Skin is a 6mm one-piece, back-entry semi-dry with a separate hood. It is available in men’s and women’s versions, and is Mares’ top-of-the-line semi-dry.

When it comes to heat-loss, wetsuits are passive, meaning that they don’t generate heat – they merely slow heat-loss.

Staying warm under water involves many factors, most of which are variable as well. Even the definitions of warm, temperate and cold water varies according to which diver you ask.

All this makes it very difficult to review a wetsuit objectively. The aim of the Mares Seal Skin is to slow heat-loss as much as possible, prolong each dive and make repeat-diving more practical. It’s a big ask.

Water robs heat 20 times faster than air. Like any other wetsuit, the Mares Seal Skin depends on the thickness and quality of the neoprene to slow heat-loss by conduction, basically heat from your body being drawn through the neoprene by the cooler water in which you’re immersed.

Then it has to prevent flushing – water entering your wetsuit, moving through it and exiting, taking your precious body-heat with it by convection. The Seal Skin depends on fit, and seals to minimise flushing.

The Design

The suit is nylon-lined inside and out. The inner lining makes it easy to slip on and off; the outer provides abrasion-resistance for the neoprene.

To prevent water entering and exiting through needle-holes, which creates heat loss, inner seams are dry-stitched and the outer ones are protected by overlaid strips of a plasticised material that seals and reinforces the external join. Mares calls this S-Seal technology.

The heavy-duty zip runs from the nape of the neck to the waistline. It is backed by a flap with a rubber-faced finish that is meant to butt up against another rubber panel to make an overlapping seal.

This helps to prevent water flushing through the zipper and carrying away heat. A small tab blocks the zip and helps prevent the zipper from undoing itself during your dive.


Glideskin is used on the neck, wrists and ankles to make a seal. Glideskin is rubber-faced, and sticks better to your skin than a nylon lining. The seal it creates is there to minimise flushing.

The suit neck has a collar with a short front zipper, which allows you to tuck in the hood bib more easily for a good seal.

0818 tests seal skin lower seal
The lower seal inverts and lies against the leg. The upper seal lies over the boot.

While the Glideskin wrist-seals lie flat against your skin, the ankle-seals invert. This means that they need to be rolled in and tucked up.

There is also a Glideskin cuff that sits over this seal. To make it easier to access and adjust the seal, the cuff has a zipper, so you can open it out.

While the ankle-seal lies under your boot, the outside cuff lies over it and seals around the boot-top to divert water-flow over the boot, instead of into it, which would give you very cold feet and create drag.

Mares has chosen to use inverted seals on the ankles but not the wrists, because gloves usually have cuffs that seal well over wetsuit wrists. Boots tend to dock less efficiently with ankle-seals.

Hoods commonly create equalisation problems, because water can’t easily get to the outer ear canal and flood it. This leads to reverse squeezes. Divers usually need to remember to pull the hood away from the face to let water into their ears to prevent this. It’s easy to forget to do it, however, as I know to my cost.

0818 tests seal skin ridges
Ridges on the forearms help to keep wrist instruments in place.

Mares has solved this problem by installing pin-holes through the neoprene adjacent to the ears to let water in. These work perfectly.

The hood has perforations to let air that might have been introduced by, for example, mask-clearing to bubble out automatically.

There’s a baffle below the holes to encourage air to leave, but cold water to stay out. As much as 50% of heat loss is through the head, so this is a smart move on a coldwater suit like the Seal Skin.

The Seal Skin combines numerous neoprene panels. These are needed to help shape the suit for a close fit, something of a problem given the fact that a stock suit has to fit a lot of body shapes within its sizing range.

I chose a size 4, but this was a little large on me, especially in the arms and legs, suggesting that I need to go to the gym to build up my biceps and calves, but keep my paunch.

In truth, getting a really well-fitting wetsuit is

a challenge these days – the answer used to be a tailored suit, but bespoke diving wetsuit-makers are pretty much extinct now. So modern suits, including the Seal Skin, use stretchy neoprene to help them to “adapt” to different builds.

An advantage is that the suit can better deal with some weight-gain and is supple, making it very comfortable to wear for long periods before, between and after dives as well as under water.

Even more flexible neoprene is used in areas that need a lot of mobility, such as around the shoulders and behind the knees. The knees have pads to protect the shins, made of Supratex, which is both supple and durable.

Along the forearms you’ll find ridges – they look like fashion strips, but they also serve to prevent wrist instruments from slipping around and up and down your arm. I was surprised to find that they work!

A clip on one thigh lets you hang the Seal Skin’s hood securely until needed. The hook tucks into a small pouch in the hood while diving. On the opposite thigh is a fitting for an optional Flexa Smart bellows pocket.


A one -piece 6mm suit is not going to provide sufficient thermal protection for long or repetitive dives in temperate or cold water by itself, although it did OK on a single 70-minute dive reaching 30m in 15°C. The Seal Skin is meant to be combined with additional protection.

Mares supplied me with two additional wetsuit accessories, a Gold Skin vest and a 2nd Skin shortie. The Gold Skin is a 2mm neoprene, zipperless vest with a nylon outer and a Gold Skin inner that is claimed to reflect lost body-heat back at the wearer.

The 1.5mm-thick 2nd Skin shortie is an unusual combination. The main body has an outer nylon finish, while the inside is rubber-faced neoprene, called Metalite, which, again, reflects back lost body-heat.

Similar to the inside of some freediving suits, this is meant to stick to your skin to virtually eliminate flushing, which is usually the greatest source of heat-loss with wetsuits.

Because the 2nd Skin has a generous front zip, it’s easy to put on when dry, but a bit of warm soapy water makes it a lot nicer to don when it’s wet and clammy!

It has a built-in Lycra hood that sits under your main wetsuit hood and has sleeves of Lycra from just above the elbow down. This prevents any restrictions on moving your arm when it’s worn under a wetsuit.

The 2nd Skin can be worn as a standalone in warm water but, having been advised by the Editor to “be careful” after revealing some of my test tactics, I didn’t want to worry him unduly by trying out the 2nd Skin on a real 15° dive by itself.

However, adding either the Gold Skin vest or/and the 2nd Skin shortie under any wetsuit, including the Seal Skin, will extend your dive time significantly.


The Seal Skin is a very comfortable wetsuit in and out of the water. The one-piece design is versatile, allowing you to layer the suit with additional shorties or undervests to meet a range of water temperatures and diving activities.


TESTER> Steve Warren

PRICES> Seal Skin Suit £318, Gold Skin Vest £54, 2nd Skin Shortie £90, Flexa Smart Pocket for SSS, £35

SIZES> SSS (Male) S2-S8, (Female) S1-S6. 2SS (Male) S2-S7, (Female) S1-S5




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