Wetsuits that use 0.5 mm neoprene layers have recently been introduced in the market. These new suits feel like Lycra but do not allow water to flow through them as what happens in suits made with the latter material. They are so thin that divers do not feel that they are wearing one. They are also very stretchy such that divers can put them on or take them off while standing. They are also form-fitting and hug divers’ bodies without forming wrinkles that pump seawater. They are so lightweight with buoyancies ranging from one to two pounds.

For years, manufacturers have tried unsuccessfully to make a suit just right for tropical diving. Looks like they finally got it right.

Maxing out the plastic for a trip to dive in warm water means you’re entitled to fantasize – swimming free as a fish, wearing naught but air cylinder and swimsuit – maybe less.

But then the reality of sunburn, jellyfish stings and fire coral sets in. And, oh year, you might want a little warmth too. Still, you don’t want to be suffocated in neoprene. You want just enough exposure protection, no more. The tropical exposure suit of your dreams is:

  • Thin – so you can forget you are wearing it.
  • Flexible – so it’s easy to put on and take off.
  • Neutrally buoyant – so you need little if any lead.
  • Warm – so you can enjoy a week in 80F water.
  • Full length – so the sun and stings stay away.
  • And hey – if it’s also lightweight, quick-drying, inexpensive and fits easily in carry-on luggage, you’re in dive-consumer heaven.

But that tropical wetsuit of your dreams has been as hard to find as the elusive giant squid. Though tropical wetsuit makers have been trying for years, their products have – until now – bombed, leaving divers either shivering or strapping on the lead.

STANDARD NEOPRENE: Back to the Quarry

Filled with nitrogen bubbles, neoprene rubber is certainly warm and can even be flexible – when thin. And there’s the rub: it is difficult and expensive to make neoprene in thin sheets. Here’s why:

Foam neoprene is formed in thick “buns,” which are sliced by sharp knives to the desired thickness. Nylon cloth is then glued to one or both sides. Because neoprene is soft, it is difficult to shave thin sheets accurately. To do it, the “scything” machine must cut very slowly, and still there are many errors and much wasted material. So, as a practical matter, 3mm has long been the thinnest wetsuit offered, with the more expensive 2mm reserved for spot uses like zipper flaps.

And 3mm or even 2mm is still not thin and forgettable. Though reasonably flexible, these thicknesses still restrict your movements considerably and still require a weight belt. Bottom line: conventional neoprene is fine for the temperate waters of a North American quarry, but definitely more of a struggle than you really want for your tropical dream.

POLARTEC SKINS: Who Are You Kidding?

Next up were the makers of Lycra skins: thin, flexible and non-buoyant. Only one problem: no thermal protection. Water flows through them almost as if they weren’t there.

This is not good. The first thing an exposure suit has to do is to keep the ocean from flowing over your skin and flushing away body heat. The best insulation in the world is useless if a suit leaks.

That’s why adding layers of fleece like Polartec and polyolefin to Lycra skins really doesn’t address the problem. Even if these miracle fibers gave you insulation when saturated with water (and it’s highly doubtful they do), the ocean still passes through the suit so easily that insulation quickly becomes irrelevant.

When manufacturers added a water-resistant barrier layer (often urethane), they were on the right track; unfortunately, it led them back to square one. The “tri-laminate” fabric (Lycra + fleece + urethane) was now as thick as 3mm neoprene and had lost most of the stretchiness of the original Lycra. The suits bagged and wrinkled when you moved, creating pumps that sucked the ocean down your neck and up your legs. Non-buoyant, yes. But cold. After a few dives, you rightfully asked: “What’s the point?”

NEOPRENE SKINS: Warm at Last?

This time, wetsuit makers seem to have gotten it right with a new, super-thin neoprene measuring as little as 0.5mm. For some perspective, one-half millimeter is about 1/50 of an inch, or the thickness of the nylon cloth glued to each side. The result: a neoprene suit that feels like a Lycra skin. That’s why we call these new suits a “neoprene skin.” They are:

  • So thin you can almost forget you are wearing anything.
  • So stretchy they don’t feel tight. You can pull them on or off as easily as a Lycra skin while standing up.
  • So form-fitting they hug your body with almost no wrinkles to pump seawater.
  • So flexible they don’t restrict your mobility. You could play tennis in one of these.
  • So light their buoyancy ranges from one to two pounds – weight you can carry in your BC pocket.
  • So quick-drying, compact and inexpensive that it’ll be tropical love at first sight.

BUT ARE THEY WARM?

In a word, yes. And the reason is simple: Water cannot pass through neoprene, even this super-thin neoprene. And because these neoprene skins conform to your body so well, water can’t easily travel up your legs and arms or down your back either. Any water that enters the suit is trapped against your skin and not pumped by wrinkles and baggy areas. So the neoprene skin prevents “flushing” better than anything short of a dry suit.

True – a neoprene skin doesn’t add much insulation, but the thin neoprene plus the thin layer of warm water trapped against your skin will be enough for many divers to stay comfortable in water down to 80F, maybe less. Add-ons like vests and beanies will extend a neoprene skin’s comfort zone without significantly reducing its advantages. Just be sure your neck is well sealed and wear head protection (see “Wear a Beanie, Baby”).

ARE NEOPRENE SKINS WINNERS?

Probably. They are still new and the number of diver-hours spent in them is still small. Long-term durability is an unknown, for example. But wetsuit makers point out that most of the resistance to tearing and puncturing of wetsuit fabric is in the nylon cloth glued to the neoprene. Nylon stretches less than neoprene and takes the strain. Since these neoprene skins can use the same nylon as thicker neoprene, they should be reasonably strong.

The Price of Plush

The use of plush liners in wetsuits provides another example of what happens when you apply thermal principles that work on land to the liquid world below.

Although a wetsuit with a comfy plush lining “feels” more toasty and huggy in the dive store, you pay a price down below: The plush lining allows more water inside the suit, resulting in more heat loss than an equivalent suit with only nylon lining on the inside.

The Water’s Like a Swimming Pool – Why Do I Get Cold?

Unfortunately, 80F water that feels warm when you’re swimming laps will feel cool when you re slowly finning past the coral, because swimming lads generates more heat than you lose to the water and relaxed scuba diving doesn’t.

Even when we never feel cold and never shiver, we are in fact gradually losing core body heat over days of repeated diving in water cooler than about 90F – unless we wear adequate exposure protection. The effect of this “silent hypothermia” is less physical and mental energy. You begin to feel sluggish and are less able to react quickly to emergencies. And you are at greater risk of DCS.

Some of this heat loss can be regained between dives through metabolism. On the other hand, it’s easy to become even more chilled in the interval between dives than in the water, If you stand in the wind, your wet akin or exposure suit will become an effective swamp cooler, chilling you by evaporation. Cover up or remove your suit and towel off between dives.

Fleece Is Warm in Air, Why Not in Water?

Because it’s the tiny bubbles of air that are trapped in the fibers of fleece fabric that insulate you, not the fibers themselves. Take that fleece sweater under water, especially to some depth, and all the air will be driven out of it. The same is true of wool and other synthetic fabrics like polyolefin. Without their bubbles of air, they have the same insulative value as wet cotton.

What about the claim that some fibers have inherent insulation value even when soaked? Some may, but we’ll never know until such a suit can be made so watertight and flexible that it doesn’t leak and pump water behind the insulation.

Water in the Suit Keeps You Warm: Fact or Fiction?

A little of both. Water is a poor insulator compared to almost any gas. But water does insulate a little-if it can be trapped in an undisturbed boundary layer against your skin. However, when water can flow through your wetsuit, in one opening end out another, it is carrying away body heat at a considerable rate.

In warm water, the small amount of insulation in the bounden/layer of water between your skin and the suit may be all you need – if you can keep it from being flushed out. So, in tropical diving, yes, the layer of water can help keep you warm.

But in colder waters you also need significant neoprene insulation. However, the amount of insulation contributed by a boundary layer of water is insignificant, even if the suit is perfectly sealed. If a leak flushes cold water through the suit, the thermal loss is significant, flushing away any hope of the boundary layer keeping your warm. So, in cold water, no, the layer of water is not an advantage.

Wear a Beanie, Baby

You really do need to keep your head warm, even in tropical water. But there’s a way to do it without the hassle of a traditional hood.

* WHY DO IT: Even without a wetsuit, your head is responsible for 20 to 35 percent of your body’s heat loss. That’s because of the large flow of warm blood that has to go to your heed to support your brain function. Most of the blood passes just below your scalp, where it is quickly chilled by its proximity with the ocean.

* WHY IT WORKS: When you begin to lose heat, your body begins to imitate a seal. It restricts the blood vessels in your extremities and near your skin in order to keep your heat in your body core. Your fingers and hands become cool and become stiff. Your subcutaneous fat layers are allowed to cool. Arterial blood carrying heat away from your body core is shunted to veins and returned to your body core before it can reach these cooler layers. They become a natural “wetsuit” for your body core, much like the sears blubber. But your brain, like bosses everywhere, believes it is too important to participate in this sacrificial cooling program and retains its full blood flow. Thus, while your body closes its other windows in order to keep in heat, this one stays wide open. You need to cover it.

* WHY WE HATE THEM: Most of what we hate about a hood comes not from the part covering your scalp, but the part around your neck end jaw. The tight neck is hard to pull over your head and restricts circulation, and the tight jaw is constricting.

* WHY A BEANIE: Shaped like a bathing cap, s beanie is easy to put on end leaves your neck and jaw free.

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