What is a wetsuit and how do you choose one? A guide to neoprene thickness
The weather’s warmed up and summer’s here. Suddenly the water is full of people on SUPs. While I was looking into sports I’d like to try one day, I started browsing online to see what gear I’d need – and one item kept coming up: the wetsuit.
First, I did some research online. Then I chatted with a few friends who scuba dive. On top of that, I went to two different water sports shops and listened to what the sales staff had to say. In this article, I want to share what I learnt.
At first glance, all wetsuits look alike. Most are black or dark blue. They’re all made of neoprene. And they all seem to have the same job: keeping you warm in the water.
But once you dig into the subject a little, you realise it’s nowhere near that simple. 2/2 mm… 3/2 mm… 4/3 mm… 5/4 mm… Some models even come with a hood.
And like me, you’re probably asking: “Which one should I buy?” As I mentioned in the Gore-Tex article, one of the biggest mistakes people make here is assuming the thickest model is the right choice for a first wetsuit.
I think that’s partly a hangover from childhood. You know how our parents always bought us clothes a size too big? “You’ll grow into it.” It’s as if the same logic is at work here. With wetsuits, though, it’s the other way round. The right wetsuit isn’t the thickest one; it’s the one that suits the sport you’ll be doing and the temperature of the water you’ll be getting into.
Does a wetsuit keep you completely dry?
A wetsuit doesn’t keep you completely dry. That’s where the “wet” in the name comes from.
Water still gets inside the suit as a very thin layer. Your body quickly warms up that thin layer of water, and the neoprene slows down contact between this warm water and the water outside, helping to keep the heat in.
So a wetsuit doesn’t completely seal you off from the water. If your dream wetsuit is one that never lets you get wet, you may be in for a small disappointment.
What is neoprene?
Most wetsuits are made from a synthetic rubber called neoprene. What makes it special is the thousands of tiny air bubbles inside it. Those air pockets are the basis of its insulation. But neoprene doesn’t just keep you warm. It also:
- Gives you flexibility.
- Offers protection against light knocks.
- Adds a little buoyancy in the water.
That’s why it isn’t only surfers who wear wetsuits, but also divers, kitesurfers, SUP paddlers and open-water swimmers.
What does 3/2 mm on a wetsuit label mean?
Now for the part that confuses people most. I remember asking “What does 3/2 mean?” the first time I saw it myself. The logic is actually pretty simple.
If the label says 3/2 mm, the neoprene on the torso is 3 mm thick and the neoprene on the arms and legs is 2 mm thick.
And the reason makes a lot of sense. Your torso is the most important area for holding on to body heat. On the arms and legs, freedom of movement matters more, so thinner neoprene is used. The same logic applies to every model, whether it’s 4/3 mm, 5/4 mm or 6/5 mm.
Is a thicker wetsuit always better?
Which brings us to the most important question. And the answer is no, of course not.
Yes, thicker neoprene will keep you warmer. But it comes with some downsides:
- It’s heavier.
- It stretches less.
- It can restrict your movement.
- It can tire you out faster.
Wearing a 5/4 mm wetsuit in the middle of summer, for example, is more likely to leave you overheating than protect you. That’s why you need to go by the water temperature rather than the air temperature when you choose.
Which raises another question: “So do we need to buy several wetsuits, then?”
You will see plenty of people who do these sports seriously using more than one wetsuit for different seasons. But for a beginner, a single model will do the job for a long time, as long as you choose it well.
Which wetsuit thickness suits which water temperature?
There are no hard limits, but these are the generally accepted guidelines:
| Thickness | Water temperature | Use |
|---|---|---|
| 1-2 mm | Tropical and warm water | Usually worn in summer |
| 3/2 mm | Roughly 17-22°C | The most popular choice among surfers and SUP paddlers |
| 4/3 mm | Around 12-17°C | A good choice for spring and autumn |
| 5/4 mm and above | Cold water | Winter; some models come with a hood |
The most important variable here, once again, is you. Some of us feel fine in 15-degree water, while others start to get cold within a few minutes at the same temperature. That’s why, at autumn races, the decision comes down to the water temperature on the day; at October events such as Oludeniz Open Water on 10 October, the sea may still be mild – or it may not.
Does the wetsuit zip system matter?
Yes. In fact, it was one of the things the sales staff I spoke to specifically pointed out. Many people focus only on neoprene thickness, but the zip system also makes a big difference to how the suit feels to use.
| Zip type | Features |
|---|---|
| Back Zip | A long zip runs down the back. Easy to get on and off, and very practical for beginners. |
| Chest Zip | The zip sits across the chest. It keeps water out better and is popular with performance-focused users. |
| Zip-Free | No zip at all. It offers extra flexibility, but it’s more of a struggle to get on and off. |
If this is your first wetsuit, I don’t think it’s essential for starting out. When you’ve only just taken up a sport, there’s no need to give it up because of your wetsuit.
Should a wetsuit fit snugly?
Absolutely. I was surprised at first by how tight wetsuits are. A friend of mine kindly lent me his wetsuit to try over a weekend, which gave me the chance to see this for myself.
It turns out that’s exactly the point. There shouldn’t be any gaps between your body and the neoprene.
When there are gaps, fresh water keeps flowing in and your body has to warm it up all over again every time. The result is that you get cold faster. So however much I love wearing oversized clothes in everyday life, when it comes to wetsuits that habit has to go. That said, it shouldn’t be so tight that it stops you breathing or moving.
What to look for when choosing your first wetsuit
The sales assistant I spoke to in the shop asked me four questions. Honestly, I thought all four made a lot of sense.
- Which sport will I be doing? Surfing, kitesurfing, SUP, open-water swimming or diving… Each sport has different demands.
- What will the water temperature be? Water temperature matters more than air temperature.
- How much will I be moving? In more active sports, flexibility comes first.
- How many times a year will I use it? If you’ll only wear it a few times a year, you don’t need to buy the most expensive pro model.
The verdict: how do you choose the right wetsuit?
If you ask me, choosing a wetsuit isn’t something to decide after reading a few reviews online. If you can, getting advice from an experienced sales assistant or from people who actively do these sports will give you a big head start.
Because the right wetsuit should be neither so thin that you get cold nor so thick that it restricts your movement.
Perhaps the most important thing to keep in mind when choosing a wetsuit is this:
A good wetsuit isn’t the one that keeps you warmest, but the one that best suits the conditions you’re in.
(And thanks to my “philosopher” friend who said this to me.) For guides to SUP, rowing, surfing and other water sports, have a look at our Water Sports category.
Choosing a wetsuit really matters in open-water races: water temperature and distance directly decide which thickness you need. You can find events you might want to enter in our open-water swimming calendar.