Best base layers for swimming in open water

Looking to add some warmth to your open-water swims without investing in a thermal wetsuit? Well, we’ve got some good news. A swimming base layer will help you do exactly that.

In fact, along with the best swimming gloves, neoprene socks and cold-water swim hats, a swimming base layer can help deliver a really comfortable open-water experience.

While many are designed to be worn under a wetsuit, they can also be worn on their own when you don’t need quite as much warmth.

But which are the best base layers for swimming? We test out a selection to find out…

Best base layers for swimming

Lomo Thermal Top

• £29 (UK only)

Made of uncoated neoprene (so not shiny or grippy) this thermal top from budget-savvy brand Lomo is made from 1mm fabric, with flatlocked stitching meaning it’s both comfortable and flexible.

Designed for watersports, it can be worn alone as an extra warm layer or under a wetsuit. We tried it under our usual wetsuit which we wear for racing, and the extra layer under the very thin arms made a huge difference to how warm our arms felt; it also kept our body warmer.

The neck sat slightly higher than our wetsuit, too, stopping any trickles!

Orca Wetsuit Base Layer Neoprene T-Shirt

• $54.99 / £55

Of all of the garments on this spread, the Orca Wetsuit Baselayer is the one we’ve easily gotten the most use out of.

We’ve worn it under wetsuits and also by itself as a single layer with a pair of shorts or jammers for warmer sea swims.

With 0.5mm underarm panels combined with top-notch Yamamoto 39 cell SCS-coated neoprene, the top is hugely flexible, comfortable and soft on the skin.

In terms of warmth, the jersey lining keeps things warm, and the long length and effective gripper on the waist hem keep water intrusion to a minimum.

For truly cold swims, we’d opt for the thicker and tighter Zone3 Neoprene Warmth Vest, but this has more versatility and is a damn sight easier to remove.

Orca Heatseeker Vest

• $71.18 / £54

Designed to be worn with or without a wetsuit on top for chillier surf or swim sessions, we found the flexibility and superb fit of the Orca Heatseeker to be a game-changer.

Easy to pull on over the head (though larger-busted swimmers may find it harder) our core was noticeably warmer when worn alone over a swimsuit or as an extra core warmth layer under our regular wetsuit.

Admittedly, it doesn’t keep your arms any warmer, which would be a benefit on longer swims, but it does have the benefit of not adding any restriction.

Zone3 Neoprene Long Sleeve Top

• $89 / £65

With so many cold-water accessories on the market, it’s worth just thinking a little about your own individual needs before splashing out – and this neoprene top is a case in point.

With long sleeves and made from 1.5mm coated Yamamoto neoprene, it ticks the boxes for warmth and hydrophobic properties. On this curvy female tester, we found that when worn over a swimsuit for added warmth it did the job, but rolled up around the waist.

It also did a superb job of adding warmth under a wetsuit, though putting both layers on together was a touch laborious!

Zone3 Neoprene Warmth Vest

• £42.50

Zone3 warned us that the Neoprene Warmth Vest was hard to get off, and they weren’t wrong: it took three people to wrestle this off us at the Long Course Weekend.

Yet this is a fantastic contender for cold-water swims, sitting tight to the body (aim to try before you buy if possible) but staying warm and unrestrictive for extended swims.

The high neck helps prevent wetsuit zip rub and, for 40-quid plus, you’re getting a titanium-coating to help maintain the body’s warmth.

Like the Orca, this doubles as a 2mm single layer for warmer swims and also adds some buoyancy for pool sets.

Roxy Rise Springsuit

• £105

Adding a splash of colour to this group test, this neoprene swimsuit from surf brand Roxy may seem an odd inclusion.

It does have a place in this test, though, as for women looking to keep their body a little warmer on short swims, a neoprene swimsuit is a great option and much easier to get on and off on chilly days, plus it won’t rise up like a vest!

We tested the swimsuit version of the Rise, but it also comes with full-length legs (£135). The 1.5mm neoprene added warmth and definitely allowed us a longer swim than just a normal swimsuit. A bit skimpy on the bum, though!

How we tested

All of the swimming base layers featured here have been reviewed by 220 Triathlon editor and open-water swim coach Helen Webster.

During testing, Helen took on multiple swims in each base layer in a range of temperatures stretching down to 7-8°C.

Each swimming base layer has been rated based on its affordability, comfort, warmth, fit and ease of getting on or off.

If a product scores over 90%, it means it’s truly a class-leading piece of kit. Anything between 80-90% also comes highly recommended, while 70-80% still represents a decent product.

Any score below 70% suggests the product has some significant flaws, but it may still be worth considering.