Drysuits: Outer wear for inner space astronauts

Trekking through outer space may not be an option for most, but inner space travel is doable for those with a diver certification card and access to a body of water. For either realm, dressing for success is not so different in that NASA’s space suits have informed scuba divers’ drysuits. Although modern versions of the drysuit have been around since the late 1980s, they remain a novel sighting for many beachgoers.

Drysuit fabric keeps water out due to waterproofing, which is woven into the fabric. Thus, I stay dry except for my head and hands, which I encase in good old neoprene (wetsuit material). By keeping most of my body dry, I can conserve heat without wasting energy warming the layer of water between my skin and the neoprene, the blubber-layer concept behind a wetsuit. A drysuit itself is only a shell, providing no warmth, so I don layers of polar fleece (pants and pullovers), not unlike others who brave inclement weather on land. And with this arrangement, I can adjust my under layers to external conditions (as opposed to juggling different wetsuit thicknesses).

A drysuit, being a complex piece of technology, comes with valves to allow for air to enter and exit the suit while keeping water out. When on the surface, I want a bit of air in the suit for floatation and comfort but not so much so that I resemble the Michelin Man.  To inflate my suit, I press on the inlet valve located on the drysuit’s upper chest area. A hose provides the conduit from the valve to the very same air tank from which I also breathe. A puff or two of air into the suit, and I’m set. To let air out of my suit (to make myself negative) when I’m ready to descend, I press on an exhaust valve found on the suit’s upper arm.

Now that I’m below the surface, there’s nothing left to do, right? Not exactly because as I sink I get heavier and heavier due to increasing outside pressure that goes hand in hand with increasing depth. I have two issues to address: One is squeeze. Visualize those food storage devices that suck out all the air in a bag (drysuit) of leftovers (diver), and you get the idea. Squeeze restricts movement and makes it hard to take a breath. The other issue is the importance of making a controlled descent, not dropping like a rock. To release the squeeze and put on the brakes to slow or stop my descent, I press the inlet valve to add air into the suit. As a bonus, the layer of air also acts as a bit of an insulator between me and the surrounding cold water.

It sounds complicated but diving in a drysuit is not unlike driving a car down the road in that staying in the lane requires continual but small adjustments. Drysuit diving also demands frequent input and output of air throughout the dive to control depth and comfort but, as with controlling a car, this becomes second nature with experience.

Another important consideration revolves around the wrist and neck openings. To keep the outside water at bay, these openings must be able to reseal themselves even under great pressure. Wrist and neck seals are commonly made of flexible latex. They don’t last very long, maybe a year. 

Lastly, there is the waterproof zipper, the gateway for diver entry and exit, and in my opinion, the crux and curse of the drysuit. A spin-off from the space program, not to be found at your local fabric store, it is arguably the most high-tech part of a drysuit. The waterproof zipper, originally developed by NASA to hold air inside astronauts’ space suits, is really a pressure zipper. Like many of the technologies developed for the space industry, divers have benefitted from the technology as well. Prior to the drysuit zipper, a drysuit really wasn’t. The drysuit zipper is really an amazing device that functions very simply. Like any zipper, it has teeth, a slide, and docking. What makes a dry zipper different (and dry) is the material the teeth are mounted to and that there are two seals, one above the teeth and one below the teeth. As I’m pulling the zipper to close the suit, the teeth behind are interlocking, which seals the inside from the outside.  This special zipper is one of the most expensive parts of the suit and seriously expensive to replace (repairs are not feasible). In fact, the zipper is one of the reasons that a drysuit costs three to four times of a wetsuit, an investment to be sure. To replace a zipper costs on the order of $400. Ouch!

This brings us to the age-old question: When is a drysuit not a drysuit? Answer: When it floods! At the end of the dive, some dampness inside the suit is expected from the diver’s respiration, perspiration, or from condensation but this humidity goes unnoticed thanks to the wicking ability of polar fleece. Unfortunately, fabric punctures, tears, or rips, and zipper failures are all causes for leaks. Yet, for the committed diver, only if they are major do they signal the end of the dive before it starts.

New drysuit technology is continually being developed. For example, I recently installed the Ti-Zip, a radical new zipper design that in my experience is superior to the single choice otherwise available. Another innovation, silicon wrist and neck seals, is a variation on the latex variety and is purported to be more heat and sunlight resistant (haven’t tried these yet). Though not yet widely available, these new inventions highlight the ongoing evolution of drysuits.

After all this explanation, is a drysuit with all its complications and expense better than a wetsuit when it comes to cold water? Speaking for myself, I would have quit diving long ago without one. The benefits of staying warmer in our local waters, which can drop into the 40s, outweigh the occasional wet arm, squishy foot, aborted dive, extra maintenance, and sticker shock. Drysuits may not be perfect but for me and many other local, inveterate divers, the alternative is unthinkable. For those who want to wear a wetsuit, I say, "Suit yourself."