The Editor says: As passionate divers, we always leap into the sea when water temperatures are high in summer — but as the dive season winds down, water temperatures drop just as fast. If you still want to get your diving fix, or catch a glimpse of rare marine life during special seasons, does that mean you're left standing on shore sighing at the waves? This time, we're republishing a piece shared by instructor 陳徵蔚 about the essentials of the drysuit, and we hope it inspires everyone to explore this unique diving specialty course! (Full article reprinted from instructor 陳徵蔚's post: 冬潛也能暖洋洋！乾式防寒衣專長介紹)
This past winter holiday, I completed a drysuit specialty instructor course.
In tropical regions, divers typically wear lightweight dive skins or wetsuits. But in Taiwan — especially along the Northeast Coast — winter water temperatures can drop below 20°C, and unless you're blessed with superhuman cold tolerance, most divers simply stay out of the water. For someone like me, though, a dive addict who feels off if I haven't jumped into the ocean for more than a week, and who can't just dash off to Kenting every other day with a full work schedule, the only real option for warm, comfortable winter diving is the drysuit.
Heat loss in water occurs 20 times faster than on land, which means some divers feel cold even in water above 25°C — which is precisely why we wear exposure protection. In Kenting, where the Kuroshio Current keeps water temperatures above 20°C year-round, a 5 mm wetsuit with a vest and hood is usually enough. But for winter diving in northern Taiwan, a drysuit is really the way to go.
Back and side views of the drysuit
A drysuit, as the name implies, keeps you dry even after you enter the water.
5 Essential Features of the Drysuit
1. Silicone Wrist Seals
The reason a drysuit keeps water out and your body dry comes down to the silicone seals at the neck and both wrists. As for the feet, the suit incorporates a fully integrated waterproof boot — but you still need to wear booties over them, otherwise you'll wear through the waterproof layer and water will seep in!
The silicone wrist seals on a drysuit
Once you zip up the long chest zipper, water is sealed out completely. The chest zipper actually has two layers: the inner metal zipper provides the true watertight seal, while the outer plastic zipper protects the metal one underneath.
That said, a drysuit keeping you dry does not automatically mean it keeps you warm!
If you wore a drysuit with nothing on underneath and jumped in, it would feel like swimming naked inside a lightweight rain poncho — you'd be absolutely freezing. The drysuit only keeps you dry; real warmth comes from the undergarments worn inside it.
Before putting on the drysuit, you can start with a base layer of thermal underwear (top and bottom), followed by a cotton long-sleeve shirt and pants, plus a comfortable pair of thick cotton socks. That's what actually keeps you warm. I look a little bulky in the photos, don't I? That's because on top of the thermal underwear, I also threw on an "extremely embarrassing" windbreaker jacket!
2. The Chest Inflation Valve
The inflation valve on the chest of the drysuit
There is an inflation valve on the chest of the drysuit, similar to the low-pressure inflator on a BCD. It connects via a hose to the first stage regulator, so you can inflate by pressing it directly. This means that when diving in a drysuit, your regulator will have five hoses attached. Once you put the suit on, the air inside affects buoyancy control, so before entering the water you'll want to purge as much air as possible from inside the suit — squeezing it tight against your body. It's a bit like vacuum-sealing a duck breast: all the air sucked out so the bag clings to the meat.
As you can imagine, that sensation is pretty constricting. This is where the chest inflation valve comes in — a small puff of air makes things considerably more comfortable. For male divers in particular, a little inflation to fine-tune the fit prevents uncomfortably excessive compression on sensitive areas.
Bear in mind that with several layers of undergarments on, and even after purging as much air as possible, the suit will still add buoyancy in the water. This means you'll need to add considerably more weight when diving in a drysuit. While the BCD remains the primary and more responsive tool for controlling neutral buoyancy, the small amount of air inside the drysuit introduces an additional buoyancy variable that you must also manage. At the same time, that air can actually work in your favour as an additional buoyancy resource. By adjusting your trim — tilting your body forward, backward, or side to side — you can shift the air pocket within the suit to fine-tune your balance. Once you get the hang of it, you'll find that a drysuit actually makes trim easier to manage than a wetsuit.
3. The Exhaust Valve on the Left Arm
The exhaust valve on the left arm of the drysuit
On the left arm of the drysuit is an exhaust valve that can be twisted like a bottle cap to release air, or pressed directly for a small burst of venting. As you descend and pressure increases, you add small amounts of air to counteract the squeeze and keep things comfortable. On the way back up, as the pressure decreases, that air expands — so you need to vent it in a controlled manner to maintain neutral buoyancy.
This exhaust valve is actually a multi-stage switch, similar in spring design to a BCD overpressure relief valve. Some divers choose to open the valve to a set position — even fully open — so that when the air inside expands, it automatically vents once the pressure exceeds a certain threshold. However, leaving it fully open carries a risk: although the valve is designed with a non-return mechanism, the spring can weaken over time, making it prone to water ingress. If water gets inside the drysuit, you're back to being tortured by icy seawater.
The great upside of a drysuit is, of course, staying dry and warm! After a dive, when you peel off the suit and the cool breeze hits, your body is completely dry — no shivering in the wind. Remaining comfortable and warm while surrounded by cold water is the drysuit's greatest advantage.
Of course, drysuits also have their drawbacks. First and foremost: cost. A drysuit starts at well over NT$40,000, with some models reaching into the hundreds of thousands — a true testament to the saying "diving ruins your life (and your wallet)!"
Second, the neck seal can feel genuinely restrictive. People with slender necks may find that any head movement causes water to seep in — another minor frustration. Overall mobility in a drysuit is a little more limited than in a wetsuit. As for putting it on and taking it off, once you're practiced, it's no harder than a wetsuit, so that's not a major issue.
4. The Male Urination Valve
A male urination valve designed for drysuits
In my opinion, the biggest downside of a drysuit is that you can't relieve yourself underwater!
Something that's completely effortless in a wetsuit becomes absolutely off-limits in a drysuit — otherwise it's essentially the same as wetting the bed.
Thankfully, the international diving community has come up with a solution: the Pee Valve. The system uses a urine collection cup connected via a catheter tube to a quick-release valve at the crotch of the suit. When nature calls, simply open the valve and you're free to go — quite literally!
The product description on the manufacturer's website reads: "Don't let nature distract you or increase your air consumption. Use this device to extend your bottom time." Indeed, if you can relieve yourself normally, the drysuit loses one of its last major drawbacks. And if you'd rather not spend the extra money on a Pee Valve, there's always the adult diaper option — it can absolutely save a desperate diver in a pinch. Though, it's fair to say, that's rather unfriendly to the environment.
5. The Female Urination Valve
A female urination valve designed for drysuits
Female divers also have a dedicated collection cup option (the She-P), which works similarly to the stand-to-pee devices like the Weepee commonly available on the market — except it naturally connects to a catheter tube and vents through the quick-release valve. Once the bathroom issue is solved, the drysuit's last critical weakness in a head-to-head comparison with the wetsuit is essentially eliminated.
From there, whether or not to learn to dive in a drysuit simply comes down to personal choice. Do you want to dive in cold water during winter while staying warm and comfortable? For older divers in particular, the sudden temperature shock of cold water flooding into a wetsuit can place significant strain on the cardiovascular system. Extended time in cold water not only raises the risk of decompression sickness (DCS), but also increases the chance of sudden cardiac events. Furthermore, if your diving ambitions extend beyond tropical destinations — if you dream of one day diving in cold water to see orcas or other cold-water species, or even learning to ice dive — then a drysuit is an obvious necessity.
In Taiwan, drysuits are primarily used during the winter months. For professional divers or those who simply can't stay out of the water, a drysuit is an excellent investment. However, since drysuit usage in Taiwan is limited to a few months each year, it's less essential for those who dive only occasionally or who head to Southeast Asia during the winter. With a high unit cost and relatively low frequency of use, maintenance and care deserve special attention. Some drysuits are single-layered, while others are double-layered (outer canvas for abrasion resistance, inner layer for waterproofing). Since the integrated boots, silicone seals, inflation valve, and exhaust valve are all replaceable components, a well-maintained drysuit can easily last over a decade.
So — is it time to invest in a drysuit and venture into cold-water diving? It just might open up an entirely new world of diving for you!
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