Most of the year, it's easy to crave sunny days, paddling bareback under your PFD in no more than a pair of boardshorts or a bikini. But for paddlers in all but tropical climates, waiting on a small (or non-existent) weather window—when water temperatures rise enough to safely paddle without proper layers—is not an option. A wetsuit is the first option to widen that window of paddling days. Where a thick fleece and windbreaker will keep you warm in cold or breezy air, a wetsuit will ensure you don’t freeze if and when you come in contact with cold water. Keep in mind, the air doesn’t need to be frigid to wear one: A warm spring or early summer day can harbor water that’s just above the freezing mark, and certain coastal or higher-latitude destinations may never have water comfortable enough to go for a swim. So for any serious paddler, a wetsuit is an important part of the kit. 

Numbers Galore: Wetsuit Thickness Explained

Wetsuits operate by a simple principle: They let cold water in, but trap it there, close to your body, which heats it. So, the more neoprene between you and the cold water, the easier it can retain that insulating layer of heat. But the warmth of thicker wetsuits, which are measured in millimeters, comes at a cost. Thicker wetsuits are obviously burlier, less flexible, heavier, and maybe even too warm in certain situations. 

Manufacturers describe wetsuit thickness in a series of one, two, or three numbers. The first (and sometimes only) number is the thickness in the chest. In a two-number sequence, the second number is the thickness of both the arms and legs. And in a three-number sequence, the second is the arms, and the third is the legs. (You may need some extra insulation in your core, but not want to sacrifice maneuverability in your arms or legs.)

Keep in mind, everyone has different temperature needs—some run hot, while others need a little extra insulation—so use this chart as a rough place to start when trying to figure out how thick of a wetsuit you need:

Wet vs. Dry Suits

When it gets really cold, your body might not have enough energy to warm up the water in your wetsuit no matter how well it seals. In that case you want a suit that seals so well that you don’t get wet at all. That would be a dry suit: a full one-piece suit made of a thick waterproof-breathable material like Gore-Tex, designed to be worn over insulting base layers where water is sealed out with latex gaskets on the neck and wrists. Consider one if you plan on kayaking glacial or high-altitude creeks and rivers, icy lakes, or otherwise frigid waters where you might end up in the water. For most paddling missions when it isn’t that cold, you might be too warm and clammy in a dry suit. 

Farmer Who? Wetsuit Profiles

Thickness isn’t the only feature that differentiates a wetsuit. They come in all different profiles and shapes, too:

• Rash guards: These aren’t technically a wetsuit, but they’re part of the package. Wear one under your wetsuit to prevent chafing or abrasion, or wear them on their own for UV protection on warm days. 
• Vests: Wetsuit vests add a little core warmth without restricting any movement on warmer days. 
• Jackets: Now with long sleeves and a zipper up the front, boosting warmth. 
• Long John: Often called a Farmer John or Jane, these combine full-length legs and a vest into one unit—they’re popular with paddlers because they provide maximum warmth without limiting any arm movement you’ll need to paddle.
• Short John: Think Long John but with shorts-length legs. 
• Full Wetsuit: The whole shebang. Full legs and a long-sleeve top in one unit. Consider paddling in one when the water temperatures drop, and certainly if you’re surfing, SCUBA or freediving, or spending any time immersed.

You can find just about any combination of wetsuits, too: Individual pants and shorts, short-sleeved shirts, etc. As a paddler, think about the other clothing you plan on wearing or layering, how and where you might be in the water, the temperature of the water, and how much (and where) you care about your paddling motion becoming restricted. Those factors will help you pick the right thickness and profile wetsuit for your on-water activity. 

Other Features

A hood is an important feature in choppy water to retain body heat and keep any cold water from splashing down your suit. You can find them attached or separate if you’re not sure about temperatures, sun exposure, or want a little more versatility. Standup paddlers may want to check out added knee padding for getting on and off boards.

Seam Construction

How the seams connect on a wetsuit has a lot to do with how much water it lets pass. Flatlock seams are stitched and allow some water in and out, but are fine for warmer temperatures. Sealed seams are first glued, then stitched. They allow much less water through and are better for colder temperatures. Finally, sealed and taped seams add a layer of exterior taping that reduces permeability and boosts durability. 

Zipper Placement

For the wetsuits that you can’t just slip on (like individual shirts or pants), you’ll find a zipper either on the back or on the chest. Chest zippers allow more overall torso flexibility and limit water getting in, but some paddlers find them more challenging to get into than back zips. Back zips can run anywhere from the full length of the back to just part of it, which limits the places water can get in and boosts flexibility, but can be harder to get into. 

Alternative Materials

Most wetsuits use a base material of synthetic rubber neoprene, though many companies integrate natural alternatives, with bases derived using less petrochemicals, such as limestone, or from more renewable resources like rubber trees. 

Wetsuit Fit

At the end of the day, the most important feature of any wetsuit is its fit, and that one differs for every user. When you’re trying a wetsuit on, keep an eye out for these things:

• If it’s a little difficult to get on, that’s OK. It should fit snug, like a glove. Some  thicker wetsuits integrate plush, insulting nylon or poly lining on the chest and back panels for added warmth, though often at the expense of stretchability. 
• If it restricts your breathing at all, keeps you from moving your arms or legs, or limits your range of motion, it’s too small. 
• Look for folds of neoprene or loose spots: You don’t want them. (Except around your armpit, which helps with range of motion.)

Keep in mind that a wetsuit will “break in” a little bit over time and will conform to your shape, so if it feels a little stiff in the beginning, that’s OK. Also consider different models and brands. One style simply may not be the perfect fit for your body type. A wetsuit that fits well always keeps you warmer and more comfortable than one that doesn’t, regardless of features. 

All articles are for general informational purposes.  Each individual’s needs, preferences, goals and abilities may vary.  Be sure to obtain all appropriate training, expert supervision and/or medical advice before engaging in strenuous or potentially hazardous activity.