So why does water conduct heat from our bodies so much faster? Water happens to be a decent thermal conductor in contrast air which is a darned good insulator. Water will conduct (or pull) heat energy from your body about 25 times faster than air of the same temperature. Keep that in mind as we consider how a wetsuit works.

Wetsuits are made from neoprene foam rubber. Neoprene foam rubber is a closed cell material. That is to say, each bubble is a closed sphere of gas, often nitrogen. It is these bubbles that give neoprene it's compressible texture. It's the bubbles that provide thermal insulation. Remember we just said that air is a darned good insulator and nitrogen, which is 79% of air, is even better.

For a wetsuit to work well certain things must be true. The neoprene must be in good condition with its bubbles intact. Wetsuits that have been on many deep bubble crushing dives will lose this property. Avid divers find that suit performance falls off significantly somewhere between 200 and 300 dives. Next the suit must fit like a second skin. Any loose material that allows water volume in the suit will diminish performance. Water as mentioned will absorb your heat from your body. As you swim that water moves and the flexing of the wetsuit will flush body warmed water out and draw cool water into the suit. This is analogous to a pastry bag pushing frosting. Any baggy sections containing water will squirt water along your body as you swim and this will carry your body heat away. If the suit is tight to your skin none of this happens. This is why it often quipped that the 3 most important things in selecting a wetsuit are fit, fit and fit. Finally the rest or your exposure protection such as a hood, gloves and booties must work in harmony with the wetsuit.

You may have come across a statement that says something to the effect of," a wetsuit creates a layer or water that your body warms and this is what keeps you warm while diving". This is misinformation. At the most a well fitting wetsuit will allow a film of wetness but it should never be a layer of water with any volume. At best your body tolerates the water or wetness in your wetsuit. Remember that water is a great conductor. It eagerly accepts your thermal energy and presents it to your suit or an opening for loss. Why do you think drysuits and semidry suits are superior thermal protection?

Everyone's tolerance to cold is unique as is his or her suit and fit. A good cold water wetsuit ensemble as described below can let many divers enjoy diving down to 50 degrees F. Dives can be made in the coldest water in a wetsuit including under the ice but this is pushing the envelope. At some point approaching 50 degrees many divers will consider using a drysuit.

As much as we talk about how to remain safe and comfortable during our dive a wetsuit's greatest limitation is often the topside experience after a dive. On a cold windy day the evaporative cooling that takes place while wearing a wet wetsuit can be brutal. When combined with the energy depletion of the dive it can become downright stressful. In poor conditions wet divers will want to get out of the wind and into dry clothes as soon as possible following a dive. As uncomfortable as getting out of the suit may be it will be worth the effort to get into dry insulating clothes. A dive parka or even a towel wrapped around you can do wonders. During a surface interval many divers will compromise by turning their suit down to the waist and wearing dry clothes on their upper body.

Getting into a Wetsuit
In order to identify a good fitting wetsuit you must try some on. If you have never been in a compressive rubber garment before you may find it a little peculiar. Let's face it most of us are not accustomed to prancing around in skin tight rubber outfits that make us look like super heroes. In order to avoid damaging a suit or experiencing personal injury let's talk about how to get into a wetsuit.

The term donning refers to getting into a wetsuit. Doffing means you are getting out of it.

For this discussion lets talk about a "full suit" or what is sometimes called a 1 piece or jumpsuit. The same principals apply to all suits styles.

• Begin my turning the legs of the suit inside out except roughly the bottom 6-8 inches.
• Put a foot down through the leg opening and get the bottom cuff up to the ball of your ankle.
• Insert the other foot in the same manner.
• With your feet now through the suit begin to roll the suit up your legs. When up to the knees stop and check the height and side to side alignment of the kneepads. Be sure these are right before proceeding.
• Now keep rolling your way up the thighs
• Wiggle it up over your buttocks
• Stop to make sure it's pulled up with a good close fit in the crotch
• Roll the suit up your belly.
• If you wish you may turn the sleeves mostly inside out and enter just as you did the legs. Otherwise you can "punch" out through the sleeves, one arm at a time.
• Be sure that the suit is worked well up onto your shoulders before attempting to zip it up.
• Using the lanyard you can zip the suit shut. Sometimes the zipper will snag on the sealing flap so when trying a suit it's best that a buddy or clerk do the zipping for you.
• Note that this description said nothing about jumping, cursing, dancing, wearing fingers to the bone or any other stressful practices.
• Sometimes you may need a little help, especially getting a sweaty diver into a dry suit. For these situations I turn to suit snot which is a 50/50 mixture of cheap "dollar store" hair conditioner and water kept in a common pump sprayer bottle. On those sticky days I will don my suit to the waist then spray my shoulders and arms and rub it around for a complete coating. This will really help you get into your sleeves and let the suit come together as you zip the back. It's rarely needed if everything is all wet or all dry.

Checking the Fit of Your Wetsuit
So there you are all zipped up in a wetsuit. How can you tell if it fits? Here are a few things to check for:

• Range of motion. It is important that you have good mobility while diving. You should be able to do the following as well with your suit on as off.
  • Put one palm on the opposite shoulder
  • Repeat for the other side.
  • Extend both arms straight up. You should not feel rubber bands pulling your arms down
  • Bend forward and touch your toes.
  • Challenge your overall mobility, you should be unhindered
• Check your breathing. The suit should not hinder your inhaling and it should not help you exhale.
• One way to check the fit in the chest area is to unzip the back of a full suit or the front of a Jacket. Now that you have been in the suit is should be well up onto your shoulders and fitting neutrally. Have your assistant zip the suit up. The zipper should not be stretching the suit material by much more than one inch. We're talking about elongation of the rubber, not just pulling it back against your skin.
• The suit should have very few wrinkles and nothing you would call a baggy sag.
• A good way to tell if the fit is snug enough is to wear if for a while, like the length of a dive. When you remove the suit your want to be able to see the imprint of the inside stitching in your skin.
• The suit should fit with a "hint of compression" is another way of describing a great fit.

Wetsuit Materials

There are many different grades of wetsuit material and each has it's own advantage. Neoprene rubber is formed in slabs and sliced to form sheets that wetsuits are made from. Vintage suits were made from un-faced neoprene rubber. This material was the rubber and nothing else it was prone to tearing. Latter for strength and ease of donning nylon was laminated to 1 or both sides. Those materials are noted as N1S and N2S indicting how many sides have nylon facing. The facing fabric may have more or less stretch depending on the blend. This will help determine the behavior of the suit. Neoprene is specified in millimeters of thickness. When you see material described as 3 mil that should read 3mm. A 3 mil suit would be paper thin. Many use mil as a slang for millimeter when in reality a mil represents a thousandth of an inch.

There are also different grades of the neoprene rubber. Some rubber is fairly rigid and as such has bubbles that will stand up better over time. Most of this material goes to high end or custom suits. Since the material does not stretch as much the actual fit is much more critical and wrist and ankle zippers are often helpful for donning and doffing. Since these materials are less compressible their buoyancy has lees swing over the course of the five.

Some suits or vests will be smooth on the inside. That is to say they are made with N1S material which get called names such as smooth-skin and glide-skin.. The smooth rubber may have some sort of finishing layer to make it easier to don and doff. The important thing is that these rubber insides will cling to your skin thus reducing any trapped water to the bare minimum. This will make for a warmer suit. By comparison the nylon faced interior of many suits will provide a means for water movement that will promote heat loss. If you have a smooth skin item wear that item against your skin and do not wear a Lycra dive skin underneath it. More about dive skins latter.

Over recent years high stretch wetsuits have become the rage. With stretch factors advertised as great as 250% they border on being one size fits all. Keep in mind that there is no free lunch when it comes to wetsuits. First of all to make the suits stretch a more compliant blend of neoprene is used. This more stretchable material will also suffer more bubble crush while under the pressure of deep water. This means it will not be as warm as a full-bodied neoprene material. Such suits generally do not hold up as well either

Wetsuit Styles

There are 2 main styles of wetsuits. For cold water they will be made all or primarily from 7mm material and will have 2 layers on your core which usually includes the groin and torso areas. This is the maximum in common wetsuits. From here you can drop layers and go to thinner materials as the water gets warmer. The principles of having your suit work effectively remain the same. What you will require for a suit is unique to you based on your metabolism, body build and tolerance to cold combined with the quality and fit of your suit.

The full suit as described is a 1 piece jumpsuit that has openings for the ankles, wrists and neck. Thickness will be either a single thickness all over or it may be thinner in the arms for mobility. In order to get adequate protection on the core a vest, often hooded is worn with the suit. The vest will usually have an attached hood but they do make them without hoods. Some of the vests run down to the navel and are usually worn under the suit. Some heavier vests have short legs and are worn over the full suit doubling up on the groin and core. For use in warmer water the vest can be omitted or the style changed. Full suits can be purchased with integrated hoods, which can also deal with the neck opening, but you need a perfect fit for one garment to work well from head to ankle. A bibbed hood can be worn, you will often need assitance in tucking these in and they do not do as well at closing off the neck opening.

This is a fullsuit, sometimes refered to as a jumpsuit or 1 piece.	The chicken vest will protect your head, close off the neck opening and mute zipper seepage. The body is often 3mm skin-in and the hood will be 5 or 7mm. This is worn under the fullsuit.	The hooded step-in vest will do everything the chicken vest does plus double up on the lower torso/groin and will usually be of 5 or 7mm neoprene. This is worn over the fullsuit.	The bibbed hood wil tuck into your wetsuit to minimize water exchange	The hooded fullsuit does a nice job of controlling seepage but finding a perfect fit may be challenging.

The other common suit style is the farmer John (or Jane) and jacket. These start with a bottom much like painters or farmers overall. This provides a first layer of neoprene on your core but the shoulder coverage is usually not much more than broad straps with a closure such as Velcro. The second layer is a long sleeved step-in jacket the doubles up on the core and groin while getting a layer on your arms. Head protection will almost always be a bibbed good or less. This style was dominant for many years.

Some divers like the John/Jane & Jacket style because they consider each garment useful for use as a separate. No doubt they do or they wouldn't say it however those uses are limited. If it's cold enough to wear a 7mm John on my legs I sure want something on my arms. If the jackets fit well over a 7mm John then there is a good chance it will be a lesser fit when worn alone. Under some conditions this may work but I do not consider it a primary decision driver.

This is the Jane for laides or the John (as in Farmer John) for men. It is a common base garment for cold water diving.	This is the jacket worn with the John or Jane. It completes the coverage of the divers body and provides 2X on the core. A bibbed hood will provide head protection		For warm water diving a shorty is sometimes worn. A long sleeve version is also available. Shortiies are commonly in the 2-3mm thickness range.

It is my opinion that a good full suit worn with an appropriate hooded vest can be the warmest, most comfortable and configurable set-up. The full suit provides the closest thing to a fill body barrier and the hooded vests will close off the neck opening and mute the seepage from the back zipper

The first suit you buy will want to be suitable for the first diving you will do. For many the diving conditions will vary over time with local seasons and travel. Here in Maine my dive wear ranges from trunks to drysuit with a 2mm shorty, 3mm full suit, 5mm full suit, 7mm full suit and a few vests thrown in between. There is no Swiss Army Knife in wetsuits, prepare to own a wardrobe eventually.

The full suit will usually be zipped up on the backside though front zip models are available. The zipper will have a sealing flap, often made from smooth skin neoprene. In some cases it is built up to provide a spine pad for comfort. Here are some other options or features:

Ankle zippers are very common and will make it easier to get the suit out of the way while putting your boots on. The suit will then go down over the boot and zip up. By putting the suit on top the water will shed over the junction and not be driven into your boots. Any ankle zipper wants to have a pleated bellows fitted behind it Made of thin neoprene it will block water flow. Some suits only have a flap, which is better than nothing. As the suit gets heavier or denser neoprene blends are chosen these zippers become more and more useful.

Wrist zippers are also seen from time to time. For practical purposes gloves are worn over the wetsuit sleeves. Unless you have uncommonly bulky hands you are better off with plain sleeves.

Some wetsuits have internal seals, sometimes called flip seals. These are rubber strips that encircle the forearms and calves. They are oriented to dam incoming water flow and will help keep warm water in and cold water out.

Face seals
Many hoods have what is termed a "trimable face seal. In order to surround your head you will see that your hood is made of numerous cleverly patterned panels. In many cases several panels form a ring around the face opening. This trimable ring will be made from N1S material that has smooth neoprene rubber on the inside and it will probably be one thickness thinner than the hood in general.

If you have such a hood it should be trimmed to your liking. If it is left untrimmed it will probably push your mask in an uncomfortable way. I like to trim mine so that it overlaps my mask by 1/4 - 3/8 inches. To do this I first don the hood and get it fitting correctly on my head. Next I don my mask. Now you use a silver Sharpie permanent marker to dot the hood right at the edge of your mask skirt. You can now remove the mask and hood. The dotted line depicts the skirt edge so sketch a line 1/4 - 3/8 inches inboard with the Sharpie. At the top of the hood there will probably be some little tie stitches on the seam. Be sure to keep one of those intact so the hood won't split on the seam. Dip your cut line down around it if needed. Using good scissors trim the material along the sketched line. If you now don the hood and mask you should be able to flip the seal up onto the mask skirt. This prevents you from getting assaulted in the forehead or temples with ice cold water. Rubbing alcohol will remove most of the remaining silver markings.

Dive Gloves
The right glove can make a huge difference in your diving comfort. Divers call dives for cold hand as much as anything and diving with cold hands is both uncomfortable and a danger as you lose dexterity. My preference is for a 5mm-gauntlet glove. The gauntlet will extend up the arm over the wrist. These extended gloves offer several advantages. First the extended overlap with the suit sleeves and the Velcro cinching strap will do a lot to limit cold water infiltration. Secondly they provide an additional layer of neoprene over your wrist where blood runs close to the skin. Warmer blood flow equals happier hands.

Your hand does not want to be restrictively tight. In fact I find that being a little loose can be a good thing. The looseness usually translates into extra volume in the palm area. Your palm warms this water volume. When you work your gloves this water is pumped to your fingers and your hands get warmed.

Dive Boots
Boots serve several important uses. First of all they help keep your feet warm. Secondly they offer mechanical protection when crossing rocks or other difficult surfaces. Buy boots carefully like any other footwear. I suggest sizing them so you can get away with adding a 1mm-neoprene sock to each foot. The extra layer will offer considerable thermal protection.

Where to Shop
Where will you buy your suit? The local dive shop is the conventional source. Another alternative is an Internet supplier. These are generally local dive shops that also do business online. BY doing a volume business they can often have attractive prices. The measurements provided in sizing charts do not tell the whole story and cuts are not consistent across brands or even models. For this reason your online wetsuit may be a poor fit. By the time you send it back and pay to have another sent in it's place you are eating into your savings. The process may also cost you 2-3 weeks. My advice to "off the rack" divers is to find a suit locally that fits you and buy it. Right there, cash & carry, case closed.

Custom Wetsuits
Not everyone can be fitted "off the rack" with a stock sized suit. The human form is very variable and it's impossible to have everyone's suit in inventory. There are a number of custom suit suppliers that fill this niche. The customer base is very diverse including full figured divers, divers with extreme proportions such as body builders and divers that want a custom pattern or other features. A suit custom built to your measurements will cost about the same as a premium off the rack suit. Considering your investment in diving this is a step worth taking. With a poor fitting suit you will be cold and dive less defeating the purpose of taking up the sport. A cold diver is also more susceptible to DCS and a host of other stresses.

Getting a custom suit involves being measured extensively. This can happen in several ways. Many companies provide a measurement drawing on their Web site. You get a cloth measuring tape and somebody measures your body in a few dozen locations. Do not try to do this yourself. A wetsuit want to fit with just a hint of compression. It will not be effective if it fits like a pair of pajamas and won't be safe if it is tight. Try to speak with the suit maker about the measuring process. When measuring around body parts should you snug up on the measure or will they subtract a little from your neutral measurement.

The second scenario involves visiting a dive shop that represents a suit maker. They will measure you and have the experience to give the maker the right inputs for a first class fit. The other good thing is that if the fit is not right you are not part of the error.

The final option is a local custom maker. Relatively few divers have this option outside of California and Florida. If you happen to be in these areas check some out. The process usually involves them measuring you. They then cut and glue the suit. You now revisit for a fitting. If alterations are needed it's a matter of a razor blade and glue. Once it's just right they add the stitching.

If you need a custom suit be sure to allow plenty of time. The process usually takes 3-4 weeks. I strongly advise you to allow an additional 3-4 weeks in case it needs to be shipped back for alterations.

Dive Skins
There is a product known as a "dive skin" this is a full body suit, generally made of Lycra. A dive skin can provide protection from the sun, scrapes and stings when diving in tropical water. Being wet fabric they offer no thermal protection

Dive skins are often sold as a wetsuit undergarment to aid in the donning of the wetsuit. They will help but with a proper fit and good technique they are entirely unnecessary. This extra layer of fabric under your suit will promote water movement. If you suit or vest has a smooth skin interior then the dive skin will defeat the purpose of this wetsuit material. I believe it is best to avoid Lycra skins for cold water diving.

There is a variation of the dive skin made from polyolefin fabric. These are said to provide added warmth on the order of an extra 2mm of neoprene and they are neutrally buoyant. Since neoprene is the driver behind the weight that you wear and the dynamic buoyancy you compensate for during your dive this is an attractive notion. I have not tried such a skin but they are highly regarded by a dive shop that I consider knowledgeable. A common brand is AeroSkin and a polyolefin skin will cost about twice the price of a Lycra version.

Another variation is the Rash Guard. This is a dive shirt made of Lycra or polyolefin. It will provide protection against your BC chaffing you as will as some sun protection.