Ask ten triathletes how to choose between a wetsuit and a swim skin, and nine will hand you the same rule: check the water temperature. Cold water, wear a wetsuit. Warm water, wear a skin. It's not wrong. It's just incomplete.
The swim leg ends at a timing mat, but your body doesn't reset when you cross it. Whatever thermal and physiological state you're carrying when you climb out of the water rides with you straight onto the bike. That's the part the temperature chart never accounts for, and it's worth more attention than it usually gets.
The Temperature Chart Is a Starting Point, Not an Answer
Temperature still matters. Blue70's own guidance is straightforward: below roughly 56-58°F, most swimmers need a purpose-built thermal suit, like the Thermal Reaction, to cover real distance without their stroke falling apart. Above roughly 70-72°F, a full suit can trap more heat than a swimmer wants to carry through a long leg.
Those numbers are a useful filter. They're not the whole decision. Put two triathletes side by side at the same start line in the same 68°F water, and they can have opposite correct answers once you factor in body composition, kick strength, sweat rate, and what's waiting for them on the bike course. A chart can't see any of that. You have to.
What a Wetsuit Actually Changes: Your Position, Not Just Your Warmth
A wetsuit's biggest swimming benefit isn't the warmth. It's buoyancy, and buoyancy changes body position. Neoprene floats. It lifts the hips and legs toward the surface, which shrinks the drag-producing cross-section you're dragging through the water. That's why swimmers at nearly every level move more efficiently in a wetsuit than without one.
Dutch researcher Huub Toussaint measured this directly in a swimming flume in the late 1980s, comparing active drag with and without a wetsuit. Most of the reduction came from the change in position, not from the neoprene surface being slick. A later study by Chatard and colleagues, published in Medicine & Science in Sports & Exercise in 1995, compared the effect across competitive pool swimmers and triathletes. The less accomplished swimmers gained more from the suit than the elite ones did.
That's not a knock on strong swimmers. It's just physics. If your hips already sit high in the water on their own, a wetsuit has less room to improve on. If they sink, you're handed a much bigger gain.
Blue70 builds that lift in deliberately. Yamamoto neoprene comes graded by cell count, 38, 39, and 40, with higher numbers meaning a more open cell structure and more flexibility, especially through the shoulders, where restriction costs you stroke efficiency long before it ever bothers your comfort. The Helix takes it further with LIFT buoyancy panels concentrated in specific zones rather than spread evenly across the suit.
A Swim Skin Isn't a Thin Wetsuit
It's tempting to think of a skin as just a lighter version of a wetsuit. It isn't. Skins are built from tightly woven or knit fabric, not foamed neoprene, and they carry essentially no buoyancy. What they're built to do is cut surface drag and hold your torso in a streamlined shape, without adding the lift or insulation neoprene provides.
That distinction should drive your decision. If you pick a skin purely because the water feels "warm enough," you're giving up the buoyancy assist without necessarily gaining anything in return, unless your body position was already strong enough that the buoyancy wasn't doing much work for you anyway. Skins reward swimmers who already move well. They don't fix a position problem. They just get out of the way for someone whose position doesn't need fixing.
Blue70's swim skin lineage traces back to the pointzero3, and the line later introduced the industry's first short-sleeved swimskin in 2016. That history tells you what the category is for: a warm-water racing tool for athletes whose technique is already efficient enough that shaving drag matters more than adding lift.
The Thermal State You Hand Off at T1
Here's the piece most buying advice skips entirely. A wetsuit doesn't keep you dry. It lets a thin layer of water in against your skin, and your body warms that layer, which is where the thermal benefit actually comes from. That means you exit the water carrying more retained body heat than a swimmer in a skin, which offers almost no insulation at all.
On a cool morning with a long, exposed bike leg, that retained heat can be a real advantage. A wet body moving at 20+ mph generates serious wind chill, and a swimmer who exits already cold feels it fast once the bike leg starts. Flip the conditions, and that same retained heat turns into a liability. A swimmer already running warm from a wetsuit-insulated swim starts the bike behind on thermoregulation, and that gap doesn't close on its own. It compounds.
This is why experienced racers sometimes make choices that look backward on paper. A strong swimmer might pick a sleeveless suit or a skin in water technically cold enough for a full wetsuit, because they know their bike leg is long and their body runs hot. Another athlete might do the opposite in genuinely warm water, choosing a sleeveless wetsuit because the pull-buoy effect through the legs matters more to them than the small drag savings, especially with a tough run still ahead. Neither choice shows up on a temperature chart. Both come from planning the whole race, not just the swim split.
Your Kick Has to Adjust Either Way
Swimmers moving into a wetsuit for the first time in a season often say their kick feels off. It is off. With the hips riding higher, the kick rate you needed for body position before can become almost unnecessary, and swimmers who keep kicking at their usual effort just waste energy fighting a position the suit has already fixed.
The reverse adjustment matters just as much. A swimmer used to wetsuit buoyancy who races a warm event in a skin for the first time often finds their legs sitting lower than expected. If the kick isn't strong enough to compensate, stroke timing and catch position shift to make up for a body position that's no longer propped up.
This is a training issue, not just a race-day one. If your goal race calls for a skin or a sleeveless suit, some of your open-water sessions should happen without full wetsuit buoyancy, so your stroke mechanics aren't tuned exclusively around a position you won't have on race morning.
Matching the Suit to the Athlete, Not Just the Water
No single factor should make this decision alone. Here's how the variables tend to stack up:
- Body composition: leaner athletes with less natural buoyancy lean toward a wetsuit; athletes who already float well can lean toward a skin
- Kick strength: weaker kickers gain more from the added lift; strong kickers can hold position without it
- Bike leg conditions: long, cool, or windy rides favor retained heat from a wetsuit; long, hot rides favor shedding that heat with a skin
- Swim experience: per the Chatard research, beginners tend to gain more from a wetsuit's buoyancy than advanced swimmers do
- Race distance: sprint and Olympic distances carry lower thermal risk; long-course races in the heat carry more
None of these override the others by themselves. A lean, weaker-kicking beginner racing a hot long-course event still has a real case for a sleeveless option like the Reaction Sleeveless or Fusion, picking up some buoyancy through the torso and legs without the heat load of full sleeves.
Check the Rulebook, Not Your Memory
Wetsuit legality cutoffs and swim skin allowances vary by sanctioning body, and they change from season to season. USAT, Ironman, and World Aquatics don't share identical rules, and a suit legal at one race series might not be legal at another. Check the current rulebook for your specific event. Don't rely on a rule you remember from last season or a different organization.
Pool swimming already went through its own version of this reckoning. After a wave of broken records in 2008 and 2009 driven by full-body, high-tech suits, World Aquatics (then FINA) restricted suit material and body coverage starting in 2010. Open-water and triathlon skins run under different, looser rules than that pool-suit era did. But the underlying point holds: fast and legal aren't the same thing, and the governing body decides where that line sits, not the swimmer.
Two Materials, Two Care Routines
Neoprene and skin fabric age differently, and treating them the same way shortens the life of both.
- Rinse your wetsuit in fresh water after every swim, whether it was salt, chlorine, or lake water, and dry it out of direct sunlight. UV exposure breaks down neoprene's flexibility over time.
- Watch your fingernails when donning. Small punctures around the ankles and underarms are the most common damage, and that kind of wear typically falls outside manufacturer warranties because it's a handling issue, not a material defect.
- Rinse skins just as consistently. They don't carry neoprene's puncture risk, but the woven fabric is vulnerable to snagging, and chlorine or salt buildup breaks down elasticity at the seams over repeated swims.
It takes two minutes after each swim. That habit is the difference between a suit that lasts several seasons and one that doesn't make it through one.
Putting It Together
Start with the water temperature as your filter, not your final answer. Then look at your bike leg: distance, expected air temperature, wind exposure. Then be honest about your kick. If you can't hold your hips up on your own, a wetsuit is doing real work for you no matter how comfortable the water feels. If your race puts you in the heat for hours after the swim, weigh that against whatever buoyancy you'd be giving up by wearing one.
Still not sure which side of that line you're on? That's exactly what a Test Swim is for. Blue70 lets you swim in a wetsuit and still return or exchange it, as long as it comes back clean, dry, and with the tags attached. Feel how a Reaction, Fusion, or Reaction Sleeveless actually changes your stroke before you commit to racing in it.
Happy swimming.
