Open Water Temperature Strategy: Wetsuit Selection for 14-25°C

The Dual Role of a Wetsuit

Many people think a wetsuit is only for warmth, but it actually serves two major functions:

1. Insulation: Reduces heat loss and prevents hypothermia
2. Buoyancy: Increases body buoyancy, saving leg-kick energy (saves 5–15% effort)

That’s why even when the water isn’t cold, triathlon rules allow wetsuits (below 25°C).

Water Temperature × Thickness Reference Table

Triathlon Rules

According to ITU (International Triathlon Union) regulations:

Water Temp	Mandatory/Allowed	Max Thickness
Below 16°C	Mandatory	5mm
16–22°C	Allowed	5mm
22–24.6°C	Allowed with time limit	5mm
Above 24.6°C	Prohibited (Elite category)	-
Above 28°C	Race cancelled	-

Recommended Thickness

Water Temp	Recommended Thickness	Suitable Body Type
14–16°C	5mm full suit + neoprene cap	Everyone
16–18°C	4–5mm full suit	Everyone
18–20°C	3–4mm full suit	Everyone
20–22°C	2–3mm full suit or short-sleeve	Those who feel cold: full suit; those who overheat: short-sleeve
22–24°C	1.5–2mm short-sleeve	Most people
24–25°C	1.5mm vest-style or none	Those with high body fat can skip it

The Three-Dimension Selection Method

Choosing a wetsuit isn’t just about water temperature; you also need to consider:

Dimension 1: Water Temperature

Baseline reference, but not the only factor

Dimension 2: Body Fat Percentage

• Body fat < 10% (lean athletes): Prone to feeling cold; can go 1mm thicker
• Body fat 10–15% (average athletes): Standard thickness
• Body fat > 20% (higher body fat athletes): Prone to overheating; can go 1mm thinner

Dimension 3: Swim Duration

• < 30 minutes: Can go 0.5–1mm thinner (won’t get cold)
• 30–60 minutes: Standard thickness
• > 60 minutes: Go 0.5–1mm thicker (longer time means higher hypothermia risk)

Advanced Wetsuit Knowledge

1. Thickness Design by Body Part

A good wetsuit isn’t uniform in thickness—it uses zoned design:

• Torso: 5mm (insulates the core)
• Thighs: 4mm (buoyancy + warmth)
• Calves: 3mm (warmth + doesn’t hinder kicking)
• Arms: 1.5–2mm (doesn’t hinder stroke)
• Shoulders: 1.5mm flexible material (range of motion)

2. Differences in SCS Coating

SCS (Super Composite Skin) is a surface coating that affects:

• No SCS: Entry-level, higher drag
• Half SCS: Mid-range, coating on the chest
• Full SCS: High-end, reduces drag by 10–15%

3. Buoyancy Distribution

The buoyancy distribution of a wetsuit affects your swimming posture:

• Higher lower-body buoyancy: Easier to keep legs up; suits those with sinking legs
• Higher upper-body buoyancy: Suits those whose legs float but torso sinks
• Even buoyancy: Standard option, suits most people

Common Wetsuit Problems

Problem 1: Feels too tight, difficulty breathing

Cause: Size too small or zipper pulled too tight
Solution: Loosen the chest area by 2 cm and do a deep-breathing test

Problem 2: Neck chafing and skin irritation

Cause: Rubber friction
Solution: Apply Vaseline or a dedicated anti-chafe balm on the neck

Problem 3: Body warms up and gets too hot after swimming for a while

Cause: High water temperature + wetsuit too thick
Solution: Unzip slightly to let water circulate in

Problem 4: Ankles stuck, can’t get the suit off after exiting the water

Cause: Ankle area too tight or swollen after soaking
Solution: Apply Vaseline on the ankles before the race; pull down firmly in T2

Water Temperature Changes on Race Day

Water temperature isn’t constant throughout the event:

Changes Within a Day

• Early morning: Coldest (1–2°C lower than midday)
• Midday: Warmest
• Late afternoon: Starts to cool down

Different Depths

• Surface 0–50cm: Exposed to sunlight, higher temperature
• 50–200cm: Moderate
• Below 200cm: Cold water layer, can be 3–5°C lower

Different Race Stages

• 30 minutes before the start: Waiting in cold water at the shore, body temperature already drops
• 5 minutes after the start: Muscles generate heat, feels warmer
• Mid-race: Body reaches equilibrium with water temperature
• Near the finish: May lose body heat due to fatigue

When Not to Wear a Wetsuit

Consider skipping the wetsuit in these situations:

• Water temperature above 24°C
• Expected swim time < 30 minutes
• Your body fat > 20%
• Short-distance races (under 500m)
• Pure swim events (no subsequent triathlon disciplines)

Training Methods

1. Test in multiple temperatures: Test your tolerance at different water temperatures
2. Long-distance testing: Swim 2km in different thicknesses during training and compare how they feel
3. Race rehearsal: One month before the race, swim the full distance with the same gear
4. Gear maintenance: Rinse with fresh water, dry in the shade, and lay flat after every use

Conclusion

Choosing a wetsuit is both science and experience. Beginners often rely on race recommendations, while veterans adjust based on their own body condition. Investing in a good wetsuit (NT$ 8,000–20,000) can last 3–5 years, offering excellent value. Train in it at least 10–15 times a year to get the most out of your gear on race day.

Related Reading

• Complete Wetsuit Rules Explained: Water Temperature Thresholds, Thickness Limits, and Whether You Should Wear One
• Open-Water Wetsuit Buying Guide: Thickness Selection, Buoyancy Assistance, and Full Tips on Putting On and Taking Off
• Wetsuit Buying Guide: Thickness, Buoyancy, and Flexibility for Triathlon Wetsuits
• The Complete Wetsuit Guide: Selection, Putting On and Taking Off, and Adjusting Your Swim Feel