WCCM Layering System
The WCCM Layering system refers to a clothing layering system taught by ATS for canyoneering as an alternative to wetsuits or drysuits. Canyoneering presents unique environmental conditions where you can quickly find yourself borderline hypothermia and in the next moment hyperthermic. A thought out layering system and understanding your own physiological needs will help overcome most of the risks associated with core-temperature control in a canyon environment.
Wetsuits are generally not encouraged as an “every-canyon” answer unless the canyon route being done is more water than walking (e.g. many of the canyons in Maui involve more swimming than anything else and a wetsuit can be practical there). Outside of canyons with excessive swimming, wetsuits work well in the water, but poorly out of the water where they serve more as a cooling device than an insulating layer.
Drysuits work well in a canyon environment (especially those drysuits with built-in relief zippers), however a drysuit will become useless very quickly if it suffers any tears and at times they can be too warm for hiking sections. Drysuits, especially the good ones (i.e. like ones with the aforementioned relief zipper) can be quite expensive. One of our friends who works for the U.S. Coast Guard has an excellent drysuit that retails for $3500.
The solution refined over the last ten years is a layering method based on the technical clothing which whitewater kayakers wear while pursuing their sport. It consists of:
A beanie for warmth. Although recent tests by the Wilderness Medicine Institute have shown that heat loss through the head is nothing exceptional when compared to the rest of the body, it still helps to insulate your head as an estimated 10% of body heat is lost through the scalp. The NRS Mystery Helmet Liner is recommended as the beanie element. Not only does it do a great job fitting to your head, but it keeps your helmet from riding too high and you look like a cosmonaut.
A fleece base layer for the top and bottom. You want to search out a midweight top and bottom fleece layer. It should be a true fleece, not a nylon/spandex blend. True fleece is a special weave made from 100% polyester. Fleece offers insulating properties whether wet or dry. Fleece when wet is not considered to be insulating however if the wind is blowing, hence the need for one layer one top that is “weatherproof”. Fleece when worn in this layering system should be placed directly against the skin. Absolutely no cotton or spandex-type shirt should be worn underneath as much of the insulating properties will be lost.
A kayak top and bottom. NRS makes an excellent drytop and drypant for canyoneering. Their good tops are made from a breathable, waterproof Tri-Ton fabric and are fitted with a neoprene waistband, neck, and over-cuffs. One example would be their Flux Drytop. 
The drypants recommended are the Blank Rock Drypant made from a combination of rip-proof cordura and a heavy-duty denier fabric called Hypro-Tex.
An insulating sock. Either a Seal Skinz Waterblocker which serves as a calf-high waterproof and durable spandex sock or for colder waters of the Sierra or New Zealand a 3-mm neoprene sock is recommended.
Depending on the ambient air temperature and canyon water temperature, layers can easily and quickly be interchanged as core-temperature preference dictates. The drytop and drypant when tucked into each other and tightened down serves as a poor-man’s drysuit, but is not dependent on the integrity of the neoprene seals for comfort due to the base layers of fleece underneath. Some water transfer will inevitably occur but it will be more of a slow-leak than a shock to the body.
Alternative options for the layering system include:
Kneepads. A form-fitting soft kneepad found in most retail stores can add a level of comfort and safety to the layering system. Kneepads will serve to protect you during any accidental slips or hidden rocks underwater while walking down canyon. Kneepads also help enclose the overall layering system helping to stave off any minor water transfer that is occurring.
Anti-Gravity Top. NRS makes a unique product called the Anti-Gravity Shirt. It’s a windproof 1-mm neoprene Mystery material with 10 pounds of imbedded flotation. This is a great top for canyons with a lot of swimming but with no moving current. Note that it serves as a supplemental flotation device and should never be worn in lieu of a proper PFD. This top be worn with any of the combination of layers, but should always be placed directly on the skin.
