Currently using a wet suit but it is too cold here in Seattle, Washington. I noticed there are neoprene dry suits and then there are shell dry suits. Which is best for cold water, and what is the difference?
Firstly, it depends your own personal "thermometer" as to how cold you get as to which type of suit to go for. They all have pros & cons. Here is a brief overview:
A Drysuit Overview
As their name implies, drysuits provide the most exposure protection by keeping water away from your skin. Their warmth lies in several things: (1) the basic thermal properties of the drysuit material itself; (2) the type & amount of garments you wear under the suit. (3) how much air you put into the suit.
Wearing a drysuit is akin to wearing a big pair of sleepers: you are encased from neck to toe in the suit, with your head & hands exposed. Most suits are back entry, which means that someone has to zip you in & out of the suit. There are a few front entry or "self donning" suits and that, with their long diagonal zipper in the front, allow you to get in & out of the suit yourself.
Drysuit Material
Basically, suits fall into 2 categories: shell or neoprene. Shells can be anything from vulcanized rubber to tri-laminates (3 layers of various materials, one of which is usually nylon). Neoprenes can be the usual 1/4" closed cell or the more exotic crushed or compressed neoprene. Fit is important in either suit: you should have a full range of motion regardless of what the suit is made from.
Shells give some protection against the temperature of the outside water; however, what you wear underneath them is the determining factor in how warm you will be. You can wear anything from a t-shirt & shorts to full "woolly bears", or multiple layers of clothing. Shell materials have minimal buoyancy characteristics, so you require less weight to be neutrally buoyant.
Regular 1/4' neoprene gives you a lot of insulation against the outside water, but it also means more inherent buoyancy. Thus, you must wear more weight to be neutrally buoyant. Again, what you wear depends entirely on how warm you want to be. Like it's wetsuit cousin, 1/4" tends to be somewhat restrictive unless fitted properly. They are usually the most economically priced suits.
Crushed neoprene is a patented product from one mfg, while some others use compressed neoprene. Because all the N2 bubbles in the neoprene have been eliminated, it has very little buoyancy of its own. It is durable, flexible, and gives more insulation than tri-lams. However, since this type of product is only available through a few manufacturers, it is very expensive.
Seals
Drysuits seal at the neck & wrists. Seals are made of two materials: latex or neoprene.
Latex is suppler, conforms well to the contours of the body, is less restrictive and so easier to adapt to & fit. However, it is also more expensive than neoprene, tears easily, is higher maintenance, and has no thermal properties (colder).
Neoprene is less expensive, very forgiving of abuse, requires less maintenance, and has some thermal properties of it's own (warmer). However, it is less supple than latex (more restrictive), and thus may takes a little longer to "get used to".
Zipper
Arguably, this is the most important and most expensive part of the drysuit. If this item "goes" it is literally HUNDREDS of dollars to replace, because of its highly specialized nature. There are particular care requirements to this type of zipper, but they are minimal and easy to incorporate into your usual routine of good equipment maintenance. Like most dive gear, if you take good care of your drysuit, it will take good care of you.
Air
If you look at the 1st stage your reg, you'll see a lot of ports. ONE is HP for your gauges, all the rest are LP for your 2nd stage, octo &, BC inflator. There are usually a couple of spare LP ports that go unused. When you have a drysuit, you connect one of these spare LP ports though a separate hose (commonly referred to as a whip) to an inflator valve on the chest of the drysuit. The hose is generally run under the right arm from the 1st stage to the valve. This is how you put air into the suit to keep you warm & for buoyancy control underwater. (You only use your BC for surface buoyancy, once underwater you only use the suit; it is much easier to control 1 buoyancy system than 2.)
Air is exhausted from the suit via a separate valve, called, appropriately enough, the exhaust valve. Current suit design usually places this on the upper left arm (bicep or tricep area). This valve is adjustable in that you will be able to determine how easily & often air is purged from the suit. Although there is too much detail to go into here about how to do this, let it be said that learning to use the suit for buoyancy control is no more complicated than using your BC; in fact, some people claim it's easier. It's just a little different!
Misc.
Generally, drysuit divers tend to need about the same amount of weight as someone diving wet in 1/4" neoprene, EXCEPT if you opt for 1/4" neoprene drysuit... air+ neoprene = more weight. Also, drysuit divers tend to need/use ankle weights, although this is not always the case. When you take a drysuit course, this will be addressed by the Instructor, who will make sure you are weighted properly as well as show you how to weight yourself in various conditions (salt vs. fresh, etc.).
Needless to say, using a drysuit requires specialized instruction from someone qualified to teach it. You didn't go diving without getting certified, did you? Well the same applies to using a dry suit!
That being said, no one who dives dry ever goes back to diving wet, except in tropical waters. Its just makes diving temperate waters so much better. So says someone from The Great White North, eh? (aka Canada.)!
Now to the BC issue: it depends on how well it fits over your drysuit. If you have one that has lots of variance in adjustability, you probably can use it with the drysuit.
Hope this helps,
~SubMariner~
