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How To Choose Your Diving Undersuit: A Guide For All Seasons

close up of diver underwater wearing a black drysuit

When it comes to drysuit diving, choosing the right diving undersuit is just as important as selecting the drysuit itself. After all, your scuba diving undersuit plays an equally essential role in keeping you warm and also works to wick away moisture and keep you comfortable when you’re in the water. 

However, selecting the best diving undersuit isn’t always straightforward, as the type you need and the layers you wear will depend on the conditions you’re diving in. Whether you’re braving the cold water through the winter like the Aquanauts team or looking ahead and upgrading some of your equipment ahead of peak diving season, we’ve put together this guide to help you choose the right diving undersuit for every season. 

What Does A Diving Undersuit Do?

First things first, it’s important to understand exactly what your diving undersuit does; this knowledge will guide you towards different features and types that may be useful to you, and ensure you’re picking the best option or layers (but more on that shortly…) for you. 

A diving undersuit is the layer worn beneath your drysuit to provide insulation and regulate body temperature while diving. Since drysuits themselves typically have very little insulating properties, an undersuit is essential for keeping warm in cold water. Your undersuit works by trapping a layer of air close to your body which acts as insulation against the cold water outside your drysuit. Additionally, a high-quality diving undersuit will wick away sweat and moisture, eliminating discomfort and preventing dampness that could make you colder. 

The Importance Of Layering

The term ‘diving undersuit’ might suggest that you need to invest in and wear just one single garment. In reality, choosing your insulation is a little more nuanced than this - but not complex, we promise! The key to finding the best diving undersuit lies in layering. The right balance between comfort, weight and insulation is key, and layering allows you to adjust your setup based on the water conditions and site you’re diving at.

Rather than wearing one single and thick diving thermal undersuit at all times, most divers find they prefer combining base layers, mid-layers, and outer thermal undersuits to create an effective insulation system. Your base layer is crucial for moisture management and, from there, you can add thermal layers depending on how much insulation is actually needed. Ultimately, this approach allows for flexibility and ensures you stay warm without sacrificing buoyancy or mobility. 

Thermal Undersuits For Cold Water Diving

Your choice of layers and scuba diving undersuit will depend largely on personal preference alongside the water temperature and specific diving conditions you plan to encounter. For cold water diving (generally below 10°C - out-of-season UK sea temperatures and below!), wearing a diving undersuit alongside your drysuit is absolutely essential. 

In these conditions, a high-performance thermal undersuit is a must-have. Top choices include the Fourth Element HALO AR and the Scubapro K2 Extreme, both of which offer exceptional insulation and warmth. We particularly recommend the former in the coldest conditions, thanks to its construction from extreme insulation ARGON aerogel which delivers lightweight and compression-resistant warmth. 

Even with a sophisticated thermal undersuit, additional base layers will still play a crucial role in managing moisture and preventing heat loss in cold waters. Combine your thicker undersuit with a base layer top and leggings from the Fourth Element Xerotherm range to benefit from compression and flexibility under a thicker undersuit. By layering effectively, you can stay warm while preventing overheating or excessive buoyancy shifts caused by bulky insulation.

fourth element halo ar undersuit

Temperate Diving Undersuits

For slightly warmer water such as UK summer sea temperatures, the focus shifts more intensely to finding the right balance between warmth and flexibility. A slightly thinner diving undersuit is preferable, but this is not to say insulation is not vital in these kinds of conditions.

Start with your high-quality base layer - the Polartec Power Stretch fabric construction of the Fourth Element Xerotherm layers will work wonders in trapping air next to the skin while remaining lightweight. From here, adding a mid-weight scuba diving undersuit like the Fourth Element Arctic is a fantastic choice. This one-piece suit provides excellent insulation with a low-profile design, preventing excessive movement of air and offering a comfortable, well-regulated dive.

fourth element arctic undersuit

Warm Weather Diving

Even in warm water, a diving undersuit is still necessary, albeit in a much-reduced form. Instead of focusing on heavy insulation, the priority shifts again to moisture management and comfort, and you can reduce your layers quite significantly by this point. 

A lightweight base layer like the Fourth Element J2 is ideal for warm-weather diving. This highly-wicking range helps to regulate body temperature by keeping moisture away from the skin while providing a light layer of insulation. If needed, you can then add a thin thermal layer on top, but in most warm water conditions, a single base layer will be sufficient. 

fourth element j2 undersuit set

Find The Perfect Diving Undersuit With Aquanauts

Picking out the best diving undersuit undoubtedly requires a good consideration of the conditions you’ll be diving in and your preferences when it comes to comfort and flexibility. Whether you’re upgrading a single layer, investing in a full undersuit system, or looking for a specialised diving thermal undersuit for the winter, the expert Aquanauts team can help you make the right considerations and find your perfect undersuit. 

With a range of high-performance scuba diving undersuits in stock and years of hands-on diving experience, we can provide you with expert recommendations and advice as you select the best diving undersuit for your next dive. Get in touch today to talk to a member of the team!