Exposure Protection

Environment: The West Coast of North America offers some of the very best diving in the entire world. The density and beauty of the life here is absolutely phenomenal. Having said that, the diving in these waters does come with it's own set of challenges. Chief among these is the water temperature. In Monterey the water rarely exceeds 54 degrees fahrenheit and it's frequently much less than that. Exposure to these water temperatures without significant thermal protection is more than just uncomfortable; it can be very harmful to your health and even fatal within a very short time.

Wetsuits: Most people learn to dive in these waters in a thick rubber wetsuit. Typically these consist of one or more layers of 7mm thick foam neoprene. These suits are not waterproof so the divers skin is in constant contact with the water. Water conducts heat away from the body very quickly which limits the effectiveness of these suits. Further, the insulating value of the suit comes from the bubbles in the neoprene. Increasing pressure at depth compresses these bubbles and reduces their insulating effect, thus a wetsuit diver gets colder as they descend. This also reduces the volume of the gas in the bubbles and makes the suit dramatically less buoyant requiring the diver to adjust their buoyancy with depth. At the surface this means wearing large amounts of lead weight to overcome the buoyancy of the suit. At depth it means adding lots of gas to their buoyancy compensator to make up for the buoyancy lost by the suit compression. At best this is annoying and at worst dangerous as it makes proper trim and buoyancy rather difficult.

Since water is the enemy of warmth wetsuits work best when they are a very close fit. This prevents water movement. Obviously you don't want the water which has been warmed by your body to be flushed out into the ocean and replaced with cold water. This tight fit in a good wetsuit can be very uncomfortable and it is not uncommon for wetsuit divers to report that they feel squeezed or even that they have difficulty breathing. Conversely a loose fitting wetsuit will fail to keep the diver warm. Finally it is worth noting that since a wetsuit diver gets wet they will continue to lose body temperature after the dive due to evaporative cooling.

Diving Dry: A drysuit solves these problems by keeping the diver, or at least most of them, completely dry. This is accomplished through the use of waterproof zippers and seals. Typically there are form fitting seals on the wrist and neck which prevent water from entering the suit. The diver's head and maybe their hands get wet but everything else stays dry. Drysuits don't fit as tightly as wetsuit so they aren't as restrictive or uncomfortable. Valves allow the diver to add or remove gas from the suit to account for the change in volume as the gas is compressed at depth. This makes diving a drysuit slightly more complex than a wetsuit but with a small amount of practice this becomes second nature and is more than worth it for the additional warmth.

Shell vs Foam Neoprene: Drysuits come in two basic flavors: foam neoprene and shell suits. Most of the cheaper suits are made of foam neoprene like a wetsuit. The actual drysuit material functions as both the insulation and as a water barrier. These generally fit tightly and have less drag underwater. They have several serious drawbacks, however. First they require a lot of weight as you have both the air trapped inside the suit and in the foam to compensate for. This limits your options for undergarments as well unless you feel comfortable with 45lbs of weight. Compression of the foam at depth will affect your buoyancy and reduce your thermal insulation. These suits are also bulky, restrictive and can take a very long time to dry. Yet another disadvantage is that over time the bubbles in the neoprene will rupture from constant compression and expansion leading to reduced thermal insulation and eventually leaks. For these reasons I don't recommend purchasing one of these suits. A better option is a shell style drysuit.

Shell suits are designed so that the water barrier and the thermal protection are separate. The outer layer or shell keeps you dry and the inner layer or undergarment keeps you warm. Depending on the water temperature you can change the undergarments to adjust your comfort level. For cold waters you might use thinsulate while in warmer waters a light fleece might be better. Shell suits also don't have an inherent buoyancy or insulation change at depth.

Materials: Shell suits are made with a variety of materials. The most common is called a trilaminate and consists of a thin layer of rubber sandwiched between two thin layers of nylon cloth. Suits made of trilaminate are light and pack easily. They also dry quickly. These suits offer no thermal insulation by themselves so you'll need warm undergarments. Trilaminate suits don't change buoyancy with depth. These suits may be a bit more fragile than neoprene suits.

There are several different grades of trilaminate material, each with its own characteristics. DUI's TLS 350 material is probably the lightest and perhaps the most water repellent meaning it drys very quickly. These suits are incredibly comfortable and great to travel with. You need to be careful around sharp objects but they seem to be quite durable. DUI TLS 350 drysuits have nearly become the DIR uniform and as such quite a few of my dive buddies are diving them. I just recently placed an order for one myself.

Diving Concepts' Ultraflex material is a bit thicker and perhaps more resistant to cutting but also heavier and it doesn't dry as quickly. My current suit is made of this material and it has so far proven to be reasonably comfortable and durable. DUI, Diving Concepts and others also offer trilaminates made of Cordura. These make somewhat more durable suits but are significantly more bulky than the lighter trilaminates and can unnecessarily restrict movement.

Crushed and Compressed neoprene have similar characteristics. Both are stretchy, comfortable and quite durable. Both have some small insulating value and don't change much in buoyancy upon descent. Which material is better depends on who's propaganda you believe. Crushed neoprene is manufactured by exposing foam neoprene to about 500 PSI (information from DUI's patent). This "crushes" all of the bubbles in the neoprene leaving a material which is thin and that doesn't compress at depth. Compressed neoprene is a dense foam neoprene manufactured with smaller gas bubbles than the foam neoprene used in wetsuits. This makes it more durable and means that it provides less thermal insulation and compresses less with depth than a wetsuit. DUI claims that compressed foam suits will wear out faster than a crushed suit because the gas bubbles will eventually collapse with repeated pressure changes. DUI detractors will tell you a "crushed" neoprene suit is effectively pre-worn out before it leaves the factory. Your mileage may vary.

These kinds of suits are less prone to catastrophic failure such as a tear from contact with a wreck but they are more prone to small pinhole leaks. They also are heavy, bulky and take absolutely forever to dry. They do tend to fit more closely than a trilam suit but any advantage in streamlining is given back by the stiffness of the material which makes it harder to move.

Vulcanized Rubber suits are commonly used by commercial divers. They are durable and don't absorb chemicals or biohazards like a neoprene suit. I'm told they are rather stiff, bulky and uncomfortable but I've never personally tried one of these suits.

Fit: Proper fit in a drysuit is important. Most suits fit much too loosely. This is largely due to the manufacturers fear of making a suit which is too small. Too large will mostly work, too small will require expensive repairs. Unfortunately a loosely fitting drysuit can cause a number of problems. Chief among these are gas trapping and dynamic instability. Simply put you want as much control over the gas in your suit as possible. Loose fitting suits also add lots of drag and can look silly in pictures.

A properly cut custom drysuit will fit very closely. Done correctly this will not interfere with range of motion or mobility. Obviously it's important that a diver be able to move freely, operate tank valves, etc. Different manufacturers have different patterns for their suits. Some work better that others. DUI's telescoping torso design allows for a form fitting suit with less material around the shoulders than other suits. If you trust your dealer to measure you properly DUI can make a suit with a "cave cut". Essentially the idea is to make a suit which fits the diver perfectly with the thickest undergarments and to remove all of the slop and fudge factor normally added to the suit to account for measuring inaccuracies.

Neoprene or Latex Seals: Wrist and neck seals can be made of either neoprene or latex rubber. Neoprene seals are more accident proof but are more likely to leak as they don't conform to the skin as well as latex. Neoprene seals also stretch over time leading to leaks. This effect is much less prominent with latex seals. Latex seals are more fragile but they seal more tightly. Since the latex seals are a bit fragile I prefer the heavy duty "double-dipped" style of seals rather than the more common standard grade seals. Some people can be allergic to latex and will be forced to use neoprene. People who don't suffer from these problems will probably want to stick with latex.

Latex seals degrade with use and should be replaced on a regular basis. If a seal starts to show cracks or become sticky it's time to replace it before it fails on a dive. Seals do best when not exposed to ozone (such as from a gas furnace or water heater), UV light, or petroleum products. Dusting the seals with corn starch or unscented talcum powder can help prolong their life and make them easier to get into and out of. KY jelly can also work as a lubricant but you should be careful not to use anything which might degrade rubber like petroleum jelly "Seal Saver" or other oils. Seals will also last longer if the suit is rinsed with fresh water after diving in the ocean.

Zippers: Drysuits are usually either back zip or self donning. Back zip suits have the zipper running across the shoulders. This keeps the length of the zipper short making it cheaper but it means you'll need help to get in and out of the suit. Self donning suits usually have the zipper running from one shoulder across the chest to the opposite hip. This makes for a longer zipper but if you're flexible enough you can get in and out of the suit yourself. Also back-zips can restrict arm movement and make valve manipulation more difficult. Zippers should be waxed periodically to keep them operating smoothly. The wax should only be applied to the outside of the zipper and not to the teeth.

P-Valve: Male divers should all have one of these. Basically it's a tube with check valves to allow you to relieve yourself underwater via a condom-catheter. While this sounds bizzare it's one of those things where once you've tried it you'll never go back.

Exhaust Valves: There are two kinds; adjustable and one atmosphere. Adjustable valves are spring loaded and you adjust the tension by twisting a knob on the top. This allows the diver to control the pressure at which gas will escape the suit on ascent. Typically they are left fully open during a dive. You can close the valve to fully inflate the suit at the surface which is nice for long boat rides. I used to be afraid of this kind of valve but my new suit has one and it works fine. My old suit has a simple check valve on the wrist. The nice thing about these valves is their simplicity. To dump air I just raise my left arm. It probably doesn't dump air as quickly as the adjustable valve and can't be closed for skiff rides.

There are 2 primary brands of exhaust valve: Apeks and SiTech. The SiTech and older Apeks "high profile" valves all work well. The newer low profile Apeks valves have developed a reputation for leaks and low flow rates. On the other hand I have on my current suit and it works just fine.

Boots: Drysuits can be fitted with several different kinds of footware. These range from a "sock" where the material covers the foot but isn't fitted wit a sole up to very heavy duty and possibly restrictive rubber boots. The sock style is usually intended to be used with wetsuit booties or "rock boots" which are shoes that go over the drysuit. Rock boots can seriously inhibit ankle movement and divers using them should take care with the laces as they can represent an entanglement or tripping hazard. Wetsuit booties usually can't be cinched down as well over the socks and can be less comfortable. Both of these options do have their merits for divers that do a lot of shore diving where wear on the drysuit feet is a significant issue.

DUI offers a boot style called a turbo sole which is a rubber sole glued onto a sock. These are very comfortable to dive but are perhaps less durable than a rubber boot. Diving concepts offers a vulcanized rubber boot on their drysuit. I have found these to be reasonably comfortable and very durable. Some other manufacturers like Andy's use a very thick rubber boot on their suits. In my experience these tend to trap a lot of gas in the feet and are overly restrictive.

Pockets: I keep a lot of gear in my pockets. Drysuit pockets are much preferable to pockets on a BC as they are more streamlined and out of the way. Since stages go on the left the left pocket is usually for things which aren't needed frequently whereas things like wetnotes and safety sausages go in the right pocket. Pockets should be of the bellows type - zippers can jam underwater and are difficult to use with gloves. Currently I have a spare mask, whistle, shears and a dive-alert in my left pocket while the right pocket has a spool, safety sausage, wetnotes and a "handle" for nose clipping stages. Pockets should have short loops of shock cord installed on each side of the top of the pocket. Items placed into the pockets are clipped off to the shock cord with bolt snaps. This keeps the pockets organized, prevents loss and facilitates easy removal of gear.

Gloves: Gloves are a bit of a controversial area. Neoprene rubber wet gloves work well if the water is not much less than 50F. Below that in my experience you'll start to have issues with both comfort and dexterity, especially on dives lasting longer than an hour. On solution is to use dry gloves, but these come with a host of issues that add both risk and complexity. For use deeper than about 100 feet dry gloves need to be equalized with the suit to prevent squeeze. This means gas needs to be able to travel from the glove through the wrist area. Also attaching dry gloves means either using latex seals on the gloves (which are impossible to don without assistance) or the use of bulky and inconvenient hard wrist rings.

Gloves probably receive more wear and tear than any other part of an exposure suit. Tears, cuts and leaks are inevitable over time. With a wet glove this isn't a big deal. Your hands are already wet and you'll merely get slightly colder. With a dry glove you now have the issue of water migrating from the gloves into the rest of the suit. Some dry glove ring systems do not retain the existing wrist seal so a glove flood means a full suit flood. This is potentially very dangerous, especially in the case of decompression diving. Other systems attach to the existing seal and allow the seal to prevent water from passing by the wrist seal. With this system gas can be equalized into the gloves by flexing the wrists to make a channel or by leaving a short piece of bungie or cord under the seal. This is to be removed if the glove floods. These systems work but are hard on the wrist seals. Care should be taken to use only heavy duty seals and to inspect and replace them as necessary. My current suit uses the Diving Concepts style rings over the existing seals. For me being able to use my fingers after a 2 hour dive is worth the hassle. People doing shorter dives may feel otherwise.

Hoods: A diver in cold water will lose a lot of warmth through their head. A good custom, close fitting hood makes a dramtic difference in comfort. Most everybody diving in Monterey these days is diving an Otter Bay Custom 9 or 12mm hood. On the subject of hoods, drysuit divers should avoid hoods with collars such as those that fit underneath a "warm collar" on a DUI suit. These make access to the neck seal difficult. In the event of a problem with the exhaust valve you may end up needing to vent gas from the neck seal and it's important that this be easily accessible.

Undergarments: This is one of the most important parts of a drysuit system. Drysuit undergarments serve two purposes. First they provide insulation which keeps you warm. Second, they wick moisture away from your body. Sweat or small leaks will make you cold in a hurry if the moisture sits on your skin. Avoid cotton since it absorbs moisture. For really cold diving a thinsulate jumpsuit like you would use for skiing works very well. Thinsulate comes in several different grades from 100 gram to 400 gram. There are also "stretch" varieties which can offer more freedom of movement at a cost of some insulation. In monterey most people will use at least 200 gram thinsulate with 400 being preferred. Thinsulate is also nice in that it traps argon and will keep you relatively warm even in the event of flood. Fleece undergarments work well for warmer water but are not recommended for Monterey. Drysuit undergarments should never be washed in detergent as this will clog up the micro pores in the material and prevent them from trapping gas and thus insulating the diver. DUI has some information on proper undergarment care here.

Inflation: Divers using air or nitrox may choose to inflate their suit with the same gas they are breathing. Air and nitrox are relatively good insulators and this keeps the diver's rig simple since no additional regulators are required. Divers adding helium into their mix will want to inflate their suit with something else as helium is a very poor insulator. Argon is typically the gas of choice for this purpose. It is both inexpensive and a very good insulator. Eric Maiken has an excellent article on the subject. Since the amount of gas needed to inflate the suit is very small a 6 cubic foot bottle will usually suffice for argon. Argon bottles can be attached to the divers rig in a variety of ways but I've found that attaching it to the left side if the backplate like this works well.

Obviously pure argon doesn't have any oxygen si breathing it is out of the question. Divers should take care to mark argon bottles carefully and to never attach a regulator with a second stage to one. Regulators without a second stage should have an overpressure relief valve installed. This will prevent hose rupture or runaway inflation if the first stage IP creeps above the rated pressure for the inflation valve or the hose.

Diving: Lastly I want to touch on the subject of diving in a drysuit. For reasons of stability and control it's important add gas to your suit only to offset squeeze and not for buoyancy control. Dave Chamberlin explains it well here here.

Hopefully this article will help you better understand the many advantages of drysuit diving and assist you in purchasing a suit. Safe and warm diving,

Clinton