What Wetsuit Thickness Do You Need For Diving In The UK?

One of the biggest misconceptions, especially among new divers, is that “it’s summer, so the water is warm.” In reality, regardless of whether the sun is shining, UK sea temperatures remain cool enough year-round to demand some kind of thermal protection.

Exactly how much protection you need depends on what you’re doing. A light, 3mm wetsuit that feels perfectly comfortable for snorkelling or an open water swim in summer could leave you shivering when it comes to scuba diving. This is because you’ll spend considerably longer underwater when diving, move around less, and lose heat more quickly as neoprene compresses with depth.

With this in mind, we’ve put together this short guide on which wetsuit thickness is best in UK waters, helping you to understand what you need to invest in and wear to get the most from your diving both now and in the future.

Why Wetsuit Thickness Matters

Before we get into the nitty-gritty, it’s worth taking the time to understand how wetsuits work and why thickness matters. Essentially, a wetsuit works by trapping a thin layer of water between your body and the suit (usually made from neoprene). Your body then warms that layer of water up, creating insulation. 

Generally speaking, the thicker the neoprene, the warmer you will stay. However, there’s more to choosing the right wetsuit thickness than simply opting for the thickest one available. Divers will typically need a thicker wetsuit than a swimmer, but it’s important to also factor in flexibility and consider alternatives (we’ll come on to those later!).

UK Water Temperatures By Season

A good way to determine the appropriate wetsuit thickness in the UK is by picking based on water temperature. You only have to think of recent heatwaves to know that air temperatures can climb well into the twenties during the summer, but sea temperatures around the UK still remain much cooler than air temperatures.

As a general guide, you can expect:

It’s also worth remembering that water temperatures can vary significantly around the UK. Locations here on the coast in Devon and Cornwall may be noticeably warmer during summer than dive sites further north, while inland dive sites will remain cooler all year round.

Which Wetsuit Thickness Should You Pick?

Let’s look in more detail at how these temperatures translate to recommended wetsuit thicknesses, or whether you’re better off looking at something different to a wetsuit entirely.

3mm Wetsuit - Best For Summer Swimming & Snorkelling

If you’re looking for a lightweight wetsuit for snorkelling and open water swimming in warmer conditions, a 3mm suit (like the Scubapro Sport 3mm - mens/womens) is a great option. Flexible and suited for situations when you’re constantly moving, you might also find a 3mm wetsuit a good pick for pool training or overseas diving in tropical waters.

However, we wouldn’t recommend a 3mm wetsuit for UK sea diving. Even in the warmest months, this wetsuit thickness will leave you feeling the cold during your dive, which could compromise both performance and safety.

5mm Wetsuit - Suitable For Open Water Swimming & Short Dives

There are some situations where you can get away with wearing a 5mm wetsuit for scuba diving in the UK, such as on shorter dives or if you’re somebody who doesn’t feel the cold as much as the average person. However, again, we’d rarely recommend this wetsuit thickness for diving in the UK.

Instead, a 5mm wetsuit offers a noticeable step up in warmth for open water swimmers hitting the water in all seasons and is great if you want to invest in one suit for multiple water activities throughout the year. 

7mm Wetsuit - Good For Regular In-Season UK Diving

A 7mm wetsuit, such as the Scubapro Definition (mens/womens) is a good sweet spot for most UK divers who do most of their diving throughout peak season. Offering significantly more insulation than a 5mm wetsuit, this is the thickness that you should look to throughout summer and autumn diving. 

To maximise warmth, we’d recommend pairing with a hood, gloves and boots, as these small additions make a surprisingly big difference to your comfort levels by reducing heat loss through your extremities. 

Alternatives To Wearing A Wetsuit For Diving

While a 7mm wetsuit is more than capable of seeing most divers through the UK dive season, it’s quite common to actually skip wetsuits altogether. Because water temperatures here are consistently pretty cool, you might prefer to just dive in a semi-dry or drysuit instead, particularly if you’re diving year-round or just prefer to stay warmer underwater.

Semi-Dry Wetsuits

Semi-dry wetsuits offer an excellent middle ground between the flexibility of a wetsuit and the insulation of a drysuit. Despite the name, a semi-dry is still technically a wetsuit, but with improved wrist, ankle and neck seals that reduce the amount of cold water that can flush through the suit.

As a result, a semi-dry wetsuit offers better thermal protection than a standard wetsuit and is a popular choice if you want to dive in the shoulder seasons as well as peak season without moving to a drysuit.

When To Wear A Drysuit Instead

That said, there’s absolutely nothing wrong with just sticking with your drysuit all year round when diving in the UK. 

Rather than relying on a layer of warmed water for insulation, a drysuit keeps you completely dry and allows you to wear a thermal undersuit underneath. This not only keeps you considerably warmer when diving, but also makes it easier to dive comfortably throughout the winter months and at colder inland sites.

So, if you’re planning to dive all year round or simply don’t enjoy the cold, we’d suggest skipping a wetsuit entirely and just investing in a drysuit that you find comfortable.

Shop Wetsuits At Aquanauts

Whether you’re looking for your first diving wetsuit or upgrading to something that might be better suited to local diving conditions, it's clear that choosing the right wetsuit thickness will make every dive more comfortable and enjoyable.

Here at Aquanauts, we stock a huge range of wetsuits, semi-dry wetsuits and drysuits, with options to suit every experience level and intended use. 

If you’re still unsure which wetsuit thickness is right for you, please get in touch with our friendly team of divers. We’re always on hand to help you work out what kind of protection you need, whether that ends up being a wetsuit or an alternative.