Whether you’re training for your first sprint triathlon or eyeing an IRONMAN finish, one of the most common questions is: What should I wear for the swim?
With terms like wetsuit, swimskin, and skins floating around, it’s easy to get confused, especially when race rules and water temperature come into play.
Here’s a simple breakdown of your options, the rules that guide them, and why choosing the right gear can give you a real edge in the water.
The difference between skins, wetsuit and swimskins
Skins (aka Trisuit or Swimwear)
Swimming in skins usually means wearing just a swimmming costume, but in the world of triathlon it's your trisuit, the one-piece you’ll wear across all three disciplines. It’s lightweight, breathable, and ideal for races where no extra swim gear is allowed, like pool-based triathlons or warm-water races where wetsuits are banned.
Swim Specific Wetsuit
A swim or triathlon-specific wetsuit is designed to help you swim faster, float easier, and stay warm. Made from smooth skin neoprene, it adds buoyancy and reduces drag, making it a go-to for most open water events and longer distance swims.
Swimskin
A swimskin is sort of a cross between the two. It's not classed as a wetsuit because it doesn’t offer buoyancy and is not made from neoprene, but it gives a performance edge by reducing drag compared to swimming in just a trisuit. It is a compressive, hydrodynamic suit worn to be worn over your trisuit during non-wetsuit swims. It’s typically sleeveless or short-sleeved, extends to the knees, and features a rear zip to reduce frontal drag and improve hydrodynamics.
What are the rules for wetsuit swims vs. non-wetsuit swims?
Whether you can wear a wetsuit in a triathlon is mostly dictated by water temperature.
Wetsuit Rules by Category and Swim Distance
Elite, U23, Junior, and Youth Athletes:
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Swim up to 1500 m:
Wetsuits are forbidden at 20°C and above
Wetsuits are mandatory at 15.9°C and below
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Swim 1501 m and longer:
Wetsuits are forbidden at 22°C and above
Wetsuits are mandatory at 15.9°C and below
Age-Group (up to 55–59 category):
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Swim up to 1500 m:
Wetsuits are forbidden at 22°C and above
Wetsuits are mandatory at 15.9°C and below
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Swim 1501 m and longer:
Wetsuits are forbidden at 24.6°C and above
Wetsuits are mandatory at 15.9°C and below
Age-Group (60–64 and older):
-
All swim distances:
Wetsuits are forbidden at 24.6°C and above
Wetsuits are mandatory at 15.9°C and below
Note: Rules may vary slightly by race organiser or federation (e.g., IRONMAN vs. British Triathlon), but this is a good general guide.
In non-wetsuit legal races, you're allowed to wear a swimskin over your trisuit, instead of wearing a wetsuit.
And for pool-based triathlons? Wetsuits are out, trisuits are the norm due to the shorter distance of these events. It is worth checking the rules of your specific race to see if you can wear a swimskin.
If the race is declared a non-wetsuit swim (and plenty of them have this season, including Challenge Roth for the first time in the event's history!) most governing bodies (including IRONMAN and British Triathlon) also ban all neoprene in the swim.
That means you can’t wear wetsuit shorts, neoprene kneeskins, shorty suits, or any other buoyant neoprene accessory. The only permissible gear in these conditions is a trisuit, or optionally, a swimskin , which must be made from textile-based, non-buoyant material.
Why Wear a Wetsuit (When Allowed)?
If it’s a wetsuit-legal swim, wearing one is almost always the smarter move, especially in open water.
Beyond the warmth, a triathlon-specific wetsuit is designed to support your body in the water, improve your position, and help you swim faster with less effort.
Many swimmers, especially beginners, tend to sink slightly at the hips and legs, which creates drag and forces the upper body to work harder to stay level. A good wetsuit uses strategically placed buoyancy panels to lift your legs and core, keeping you in a more horizontal, streamlined position. This is closer to how elite swimmers naturally float and means less energy is wasted fighting your own body mechanics.
So, a wetsuit can make the swim leg feel more controlled and less draining.
Buoyancy Boost : A wetsuit helps your body stay higher in the water, reducing effort and improving stroke efficiency.
Reduced Drag : Swim wetsuits have sleek outer coatings aka smoothskin neoprene and the tight fit of the wetsuit make it glide through the water faster than bare skin or textile.
Energy Conservation : A streamlined position in the water means you’ll exit the water less fatigued and more ready for the bike and run.
Confidence : Especially for beginners, the added flotation can ease anxiety of being in the open water and improve your mental game.
Why Use a Swimskin (When Wetsuits Are Banned)?
When wetsuits aren’t allowed due to warm water temperatures, many athletes are left deciding between swimming in just a trisuit or upgrading to a swimskin.
While it might seem like a small difference, a swimskin can offer meaningful performance gains, especially over longer distances. Designed for speed, not warmth or buoyancy, swimskins reduce drag and help you glide through the water with less resistance.
Swimskins are built from tightly woven, water-repellent fabrics that sit flush against the body, minimising drag caused by loose or absorbent materials like a trisuit.
While they don’t offer buoyancy like a wetsuit, they significantly reduce surface friction, especially around the hips, shoulders, and thighs, where water resistance can otherwise slow you down.
Over 750m, 1.5km or 3.8km swims, even small reductions in drag can add up to measurable time gains. For athletes chasing every second, that’s a real advantage.
Sleek Hydrodynamics : Swimskins compresses your body and smooths your profile to help reduce resistance.
Improved Speed : While swimskins won’t float like a wetsuit, it’s proven to shave seconds off your swim compared to wearing just a trisuit.
Muscle Support : Swimskins offer gentle compression, which can reduce muscle vibration and fatigue over the course of your swim.
