Last week a familiar argument flared up in a triathlon chat. An age-grouper swims 1:45 per 100 m in the pool and 1:45 in open water too — with a wetsuit and without. The conclusion seemed obvious: “a cheap wetsuit does nothing”. Then the hot water was switched off at his pool, he swam in his wetsuit in a 50-metre pool — and clocked 1:30. That is 15 seconds faster per 100.

So does a wetsuit make you faster or not? The research says it does, but the effect varies enormously — and the biggest winners are the weaker swimmers.

Why a wetsuit makes you faster

Neoprene is foamed rubber full of tiny gas bubbles, which is why it floats. There are three effects:

Buoyancy. The hips and legs rise and the body lies flatter. For anyone whose legs “sink”, this is the main gain.
Less drag. A flatter body means a smaller frontal area. The smooth surface of neoprene also cuts friction a little.
A longer stroke. Travelling further with each stroke, the swimmer spends less energy for the same speed.

What the research shows

Chatard's classic study (Medicine & Science in Sports & Exercise, 1995) compared two types of athlete head to head. 8 competitive swimmers and 8 triathletes swam 400 m with and without a wetsuit.

Swimmers: 4:12.5 in a wetsuit versus 4:13.9 without — the difference was not statistically significant.
Triathletes: 4:45.8 versus 5:04.7 — 19 seconds faster (p < 0.01), about 6%.

The gain was larger the more the suit lifted the athlete (r = 0.63). The authors concluded that a wetsuit helps most of all inefficient swimmers with poor buoyancy who swim slowly.

Gay and colleagues (IJSPP, 2020) tested 33 swimmers over 400 m in a 25-metre pool: in a wetsuit they were ~6% faster. The gain came from stroke length (+4%), while maximal heart rate and lactate did not change — the same effort produced more speed.

A review by Quagliarotti and colleagues (IJSPP, 2021) pooled 17 studies: speed improved by up to 11%, but the size of the effect depends heavily on the swimmer's level, the suit model and how used to it the athlete is. The authors candidly call the effect size “debatable”.

The same group in 2023 had 11 experienced triathletes swim 7 × 200 m at the same speed with and without a wetsuit. In the suit the body lay flatter, there were fewer strokes and breaths, heart rate and perceived exertion were lower, and by the end of the set the triathletes were less fatigued.

Sleeves or sleeveless

Lim and colleagues (Journal of Strength & Conditioning Research, 2024) compared 14 people at the same pace (80% of VO2max) in four setups: regular swimwear, neoprene shorts, a sleeveless wetsuit and a full-sleeve wetsuit.

Swimming at the same speed without a wetsuit was the most expensive in terms of oxygen.
Sleeved and sleeveless wetsuits turned out to be equally economical — no difference was found on any measure.
Neoprene shorts were in between: more economical than swimwear but worse than a full suit.

Stroke rate and stroke length did not change in this study — the gain came from buoyancy, not technique.

Why the gain seems to vanish in open water

The story from the chat has a simple explanation: the pool and open water compare different things.

Turns. In a 25-metre pool every 100 m includes 3 turns with a push-off and glide; in a 50-metre pool, 1. In open water there are no push-offs at all.
Sighting. Every time you lift your head, it breaks your body position and disrupts your rhythm.
Distance. GPS in open water is off by tens of metres: the watch only picks up satellites when your arm is out of the water. We covered in detail why watches get distance wrong. Pace from your watch in open water is an estimate, not a measurement.
Conditions. Current, waves and wind change even within half an hour.

There is only one fair comparison: the same stretch of open water, on the same day, with and without a wetsuit, at the same perceived effort. Ideally, several times.

Limitations

Almost all studies were done over short distances in a pool. How the effect carries over to 1.9 or 3.8 km in a lake has barely been studied.
The samples are small: 8–33 people.
In 2026 Afanasyeva and colleagues (International Journal of Exercise Science) swam 700 m in a warm lake (about 28 °C) with and without a wetsuit: faster in the suit (742 versus 908 s), with no overheating. But there were only four participants.

How to apply this

If you came to triathlon from outside swimming and your legs “sink” in the water, a wetsuit will give you the most. For you it is a direct saving of energy before the bike leg.
If you are a former swimmer, the gain may be minimal. Comfort decides: a suit that is tight in the shoulders can cost you more than its buoyancy gives back.
Nobody has compared cheap and expensive models directly. Judging by the mechanism, what matters most is buoyancy and fit. Expensive models usually win on shoulder flexibility and comfort.
Train in your wetsuit. At least 3–4 sessions before the race: the suit changes your body position and you need to get used to it. The 2021 review explicitly names familiarity as one of the factors behind the effect.
Do not carry your pool pace over to open water — with a wetsuit or without. Plan the swim leg by feel and heart rate, not by the pace on your watch.
Check the race rules. Under World Triathlon rules a wetsuit is mandatory or forbidden depending on water temperature: in cold water it is mandatory, in warm water it is not allowed.

The bottom line

A wetsuit makes you faster by ~6% on average, and by up to 11% at most.
Strong swimmers may gain nothing, while triathletes with poor buoyancy gain up to 19 seconds per 400 m.
Sleeved and sleeveless wetsuits are equally economical.
In open water the gain is masked by pool turns, sighting and GPS error — compare only on the same stretch on the same day.

Sources: Chatard J.C., Senegas X., Selles M., Dreanot P., Geyssant A. “Wet suit effect: a comparison between competitive swimmers and triathletes”. Medicine & Science in Sports & Exercise, 1995;27(4):580–586. PMID: 7791590 · Gay A., López-Contreras G., Fernandes R.J., Arellano R. “Is Swimmers' Performance Influenced by Wetsuit Use?”. International Journal of Sports Physiology and Performance, 2020;15(1):46–51. DOI: 10.1123/ijspp.2018-0891 · Quagliarotti C., Cortesi M., Gatta G. et al. “Wetsuit Use During Open Water Swimming. Does It “Suit” Everybody? A Narrative Review”. International Journal of Sports Physiology and Performance, 2021;16(9):1217–1224. DOI: 10.1123/ijspp.2020-0808 · Quagliarotti C., Cortesi M., Coloretti V. et al. “The Effects of a Wetsuit on Biomechanical, Physiological, and Perceptual Variables in Experienced Triathletes”. International Journal of Sports Physiology and Performance, 2023;18(2):171–179. DOI: 10.1123/ijspp.2022-0029 · Lim B., Villalobos A., Mercer J.A., Crocker G.H. “Energetics and Basic Stroke Kinematics of Swimming With Different Styles of Wetsuits”. Journal of Strength & Conditioning Research, 2024;38(10):1793–1799. DOI: 10.1519/JSC.0000000000004866 · Afanasyeva K., Swafford A., Navalta J.W., McGinnis G.R., Mercer J. “Brief report of core temperature patterns in triathletes while swimming in warm open water with and without a wetsuit”. International Journal of Exercise Science, 2026;19. DOI: 10.70252/ijes2026605