It's 7am at the beach. You've got the wetsuit. You've got the kid. And now you're standing there wondering: do they wear something underneath? A rashie? Bathers? Just... nothing?
You're not alone. It's one of the most googled wetsuit questions in Australia, and the answer is genuinely useful — because getting it right means your kid stays warm, comfortable, and in the water for longer. Getting it wrong means chafing, cold, or the dreaded "I want to go home" twenty minutes in.
Here's the complete guide.
The Short Answer
Most kids wear their regular swimsuit or bathers under a wetsuit. In warm water above 20°C, that is all they need. In cooler water below 18°C, adding a thin rash vest underneath provides extra warmth without adding bulk. The key is avoiding cotton, which holds water and chills quickly.
For most Australian conditions: a rashie underneath is the sweet spot. It prevents chafing, adds sun protection, makes the wetsuit easier to get on and off, and keeps the kid comfortable throughout the day.But the full answer depends on water temperature, wetsuit type, and how long your kid plans to stay in.
What to Wear Under a Wetsuit: Your Options
The main options for wearing under a kids' wetsuit are regular bathers, a rash vest for extra warmth, or nothing at all. Swimsuits work best for most conditions. Rash vests add a thermal layer in cooler water. Going bare underneath suits warm water and reduces bunching. Avoid cotton entirely.
Option 1: A Rashie (Best All-Rounder for Kids)
This is the most recommended option for children, and for good reason.
A rashie under the wetsuit:
- Prevents chafing — creates a barrier between neoprene and skin, especially at the neck, underarms, and behind the knees (the worst friction points)
- Adds UV protection — a UPF 50+ rashie blocks 98% of UV radiation, giving extra coverage in case the wetsuit comes off during the day
- Makes getting in and out easier — the fabric acts like a lubricant between skin and neoprene, reducing friction
- Simplifies the day — your kid can strip the wetsuit off and still be in a rashie for rock pools, beach play, or lunch
A standard lycra rashie won't add much warmth on its own — it's primarily an anti-chafe and sun protection layer. But it does reduce water flushing inside the suit, which helps maintain the warm water layer that keeps your kid comfortable.
Option 2: Nothing (Bare Skin)
Perfectly fine in warm water (above 22°C) with a well-fitting wetsuit. Most experienced surfers wear nothing underneath.
When it works: Short sessions in warm water, a wetsuit with smooth interior lining, and no history of chafing. When it doesn't: If your kid is prone to rash on the neck or underarms, if the session is long, or if they'll be getting in and out of the wetsuit multiple times throughout the day.Option 3: Bathers / Swimsuit Underneath
A common parent choice, and it works — with some caveats.
Pros: Prevents chafing, adds modesty when removing the wetsuit in public, and provides a hygienic barrier. Cons: Swimwear can bunch up under the suit, especially board shorts, which ride up and create lumps. Bulky seams, ties, or hardware dig into skin under neoprene compression. If you go this route: A simple one-piece or bikini bottom works best. Avoid board shorts underneath a wetsuit — they're too bulky.Option 4: Thermal Base Layer (Cold Water Only)
For water below 15°C — or for kids who feel the cold more than most.
Best materials:- Polypropylene: Lightweight, manages moisture, traps air
- Polyester / hydrofleece: Quick-drying, breathable, purpose-made for under wetsuits
- Thin neoprene underlayer (0.5–1mm): Reduces water flow, significant heat retention
- Merino wool: Naturally insulating, temperature-regulating
The key: any base layer should be snug without restricting movement, with flat seams and no zips, buttons, or velcro.
What NOT to Wear (Ever)
- Cotton. Absorbs up to 27 times its weight in water. Holds moisture against the skin. Gets heavier, colder, and more abrasive the longer it's wet. Does the exact opposite of what a wetsuit is designed to do.
- Loose clothing. Bunches under the suit, ruins the fit, prevents heat retention.
- Traditional underwear. Not designed for water, bunches up, doesn't dry quickly.
- Anything with hardware. Zips, buttons, and velcro dig into skin under neoprene compression.
The Temperature Guide: What Kids Need by State
Children lose heat faster than adults — that's physics, not personality. Kids have a larger body-surface-area-to-mass ratio, meaning they lose heat to the environment much faster relative to the amount of heat stored in their body. Less body fat for insulation. Less capacity to self-regulate temperature.
Rule of thumb: If an adult is comfortable in a particular wetsuit setup, a child will typically need one level more protection.Australian Water Temperatures by Season
| State | Summer | Autumn | Winter | Spring |
|---|---|---|---|---|
| QLD (Gold Coast) | 25–26°C | 23–25°C | 21–22°C | 22–23°C |
| NSW (Sydney) | 22–25°C | 20–22°C | 17–19°C | 19–20°C |
| WA (Perth) | 22–24°C | 21–22°C | 18–20°C | 19–20°C |
| SA (Adelaide) | 19–21°C | 17–19°C | 14–16°C | 15–17°C |
| VIC (Bells Beach) | 18–21°C | 16–17°C | 11–14°C | 14–16°C |
| TAS (Hobart) | 15–17°C | 14–16°C | 12–13°C | 12–14°C |
What to Wear at Each Temperature
| Water Temp | Wetsuit | What Underneath | Accessories |
|---|---|---|---|
| Above 24°C | Rashie only (no wetsuit) | N/A — sun protection is the priority | Hat, sunscreen |
| 20–24°C | Springsuit (2mm) | Nothing or rashie for chafing | None needed |
| 18–20°C | Springsuit (2mm) or light steamer (3/2mm) | Rashie underneath recommended | None needed |
| 15–18°C | Steamer (3/2mm) | Rashie underneath | Optional booties for reef/rocks |
| 12–15°C | Steamer (3/2mm or 4/3mm) | Thermal base layer recommended | Boots (2–3mm) |
| Below 12°C | Steamer (4/3mm+) | Thermal base layer essential | Boots + hood. Gloves below 10°C |
- Gold Coast and North QLD: A rashie is enough most of the year. Springsuit in winter.
- Sydney and Perth: Springsuit in summer, steamer with rashie underneath in winter.
- Melbourne and Adelaide: Steamer year-round (except summer). Thermal base layer and boots in winter.
- Tasmania: Steamer year-round. Thermal base layer, boots, and hood in winter.
The Chafing Problem (And How to Fix It)
Wetsuit chafing happens when the suit rubs against bare skin, especially around the neck, underarms, and inner thighs. Prevent it by ensuring a snug fit with no loose material, applying anti-chafe balm to friction points, and wearing a thin rash vest underneath as a barrier layer.
Wetsuit chafing is the number one reason kids don't want to go back in the water. It's also completely preventable.
Where it happens: Neck (the worst spot), underarms, inner thighs, wrists, ankles, behind the knees. Why it happens: Friction between neoprene and skin, made worse by salt water and repetitive movement. How to prevent it:- Wear a rashie underneath. The single most effective solution. A thin layer of fabric between neoprene and skin eliminates most chafing.
- Apply anti-chafe balm. Water-based products like Body Glide, applied to the neck and underarms before suiting up. Never use petroleum jelly (Vaseline) — it degrades neoprene.
- Check the fit. A wetsuit that's too loose creates excess movement and friction. Too tight creates pressure points. The neck seal is the most important area — it should be snug but not restrictive.
- Rinse after every use. Salt and sand residue build up inside the suit and create additional abrasion next time.
How to Get a Kid Into a Wetsuit (Without Tears)
The easiest method is the plastic bag trick: put a plastic bag over each foot before sliding legs in, then remove the bags. Pull the suit up in stages — legs first, then torso, then arms. Use the inside-out technique for arms, and never yank the neckline over the head.
If you've ever tried to wrestle a resistant child into a wetsuit, you know this section exists for a reason.
The plastic bag trick: Put a plastic bag over each foot before sliding it into the wetsuit leg. Reduces friction instantly. Pull the bag out once the foot is through. Works for hands too. Dampen the inside: A bone-dry wetsuit is harder to put on. A quick spray of fresh water inside the legs and arms dramatically reduces friction. Put the rashie on first: A thin base layer acts like a built-in lubricant between skin and neoprene, making everything slide more easily. Apply anti-chafe balm to the neck: The neck seal is where most kids get stuck. A quick application of Body Glide before pulling it over the head makes entry much smoother. Try putting it on in the water: Wade in with the wetsuit loosely on and pull it up in the water. The water breaks the seal wherever it's sticking.How to Know If Your Kid Is Too Cold
Watch for shivering, blue or pale lips, goosebumps that do not go away, and unusually quiet behaviour. Kids often will not tell you they are cold. If their skin feels cold to touch when you check their torso under the wetsuit, it is time to get them out of the water.
Kids are unreliable narrators about their own body temperature. They will say "I'm FINE" through blue lips while shivering. Here's what to watch for:
Early signs (get them warm soon):- Shivering
- Blue or purple lips and fingertips
- Persistent goosebumps that won't go away
- Going unusually quiet (cold kids often go silent before they complain)
- Slurred speech or confusion
- Loss of coordination, clumsiness, fumbling
- Growing more vertical in the water (unable to maintain horizontal position)
- Shallow breathing, extreme tiredness
- Babies under 12 months: 10–15 minutes
- Toddlers: 20–30 minutes
- Older children: Monitor continuously — blue lips or shivering means out immediately, regardless of time
After the Water: The Afterdrop Effect
Here's something most parents don't know: your child's body temperature continues to drop for 30–45 minutes after leaving the water. It's called "afterdrop" — cold blood from the extremities returns to the core, and a child who felt fine getting out can be significantly colder 15 minutes later.
What to do:- Remove the wetsuit and dry off immediately. A towelling poncho or hooded towel is ideal for kids — pulls over the head, allows changing without drama.
- Warm layers on. Fleece, warm socks, beanie, jumper. Start with the upper body first.
- Hot drink. A thermos of hot chocolate waiting in the car is bribery, and it works.
- Keep moving. Beach sprints, star jumps — movement generates internal heat.
Why Fit Matters More Than Thickness
A well-fitting wetsuit outperforms a thicker but poorly fitting one every time. Gaps let cold water flush through, eliminating insulation. A snug 2mm springsuit that sits flush against the skin keeps a child warmer than a loose 3mm steamer with water pooling at the lower back.
Here's the most important thing to understand about wetsuit warmth: a perfectly fitting 3/2mm suit will keep your child warmer than a loose 4/3mm suit.
Wetsuits work by trapping a thin layer of water between the suit and the body. The body heats this layer, and the closed-cell foam insulates it from the cold water outside. If the suit is too loose, cold water constantly flushes through and replaces the warm layer. The wetsuit might as well not be there.
The critical fit points:- Torso: Should be snug with no excess material. This is where the most heat is retained.
- Neck: Snug seal to prevent water entry. The neck is the biggest point of water flushing.
- Wrists and ankles: Close-fitting to prevent constant cold water exchange.
- One size up is okay if the torso still fits well. More than that, and warmth performance drops significantly.
At AVALY, our wetsuits are made from Yulex plant-based natural rubber — which has the same closed-cell foam structure as neoprene, trapping millions of sealed gas-filled cells that insulate against heat loss. Independent testing found Yulex maintained the highest average body temperature across eight monitored body regions when tested against four other wetsuit brands in 10°C water. Same warmth, 80% less CO₂.
Quick Reference: What to Wear Under a Wetsuit
| Situation | What Underneath | Why |
|---|---|---|
| Summer surf, warm water | Nothing or rashie | Comfort and sun protection |
| All-day beach trip | Rashie | Easy transitions between wetsuit and beach play |
| Chafing-prone kid | Rashie + anti-chafe balm on neck | Prevents irritation at all friction points |
| Cool water (15–18°C) | Rashie under steamer | Reduces flushing, adds comfort |
| Cold water (12–15°C) | Thermal base layer under steamer | Real warmth addition needed |
| Very cold (below 12°C) | Thermal base layer + accessories | Base layer, boots, hood essential |
| Toddler in any wetsuit | Swim diaper + rashie | Hygiene and comfort |
---
Frequently Asked Questions
Should kids wear a rashie under a wetsuit?
In most situations, yes. A rashie is the best all-round choice for kids because it prevents chafing (especially at the neck, underarms, and behind the knees), adds UV protection, and makes the wetsuit easier to get on and off. It won't add significant warmth, but it reduces water flushing inside the suit, which helps maintain comfort.
Can you wear nothing under a wetsuit?
Yes — in warm water (above 22°C) with a well-fitting wetsuit, bare skin is perfectly fine. Most experienced surfers wear nothing underneath. For kids, a rashie is still recommended because it prevents chafing and simplifies the day (they can keep it on between activities).
What should you NOT wear under a wetsuit?
Never wear cotton — it absorbs up to 27 times its weight in water and makes you colder. Avoid loose clothing (bunches and ruins the fit), traditional underwear (bunches and doesn't dry), and anything with zips, buttons, or velcro (digs into skin under neoprene compression). Board shorts are too bulky under a wetsuit.
How do I know if my child's wetsuit is too loose?
If you can fit more than a flat hand between the suit and your child's torso, it's too loose. Signs during use: the child gets cold quickly despite adequate thickness, you can see water flowing in and out at the neck or ankles, and there's excess material bunching at the lower back or behind the knees. A well-fitting wetsuit should be snug at the torso, neck, wrists, and ankles.
What temperature do kids need a wetsuit in Australia?
Most kids need a wetsuit below 22°C for any extended time in the water. A springsuit (2mm) works for 18–22°C. A steamer (3/2mm) is needed below 18°C. For Victorian, Tasmanian, or South Australian winter (below 15°C), a 3/2mm or 4/3mm steamer with a thermal base layer is recommended. Kids lose heat faster than adults, so err on the warmer side.
Do kids need wetsuit boots in Australia?
Boots become important below 15°C — which means Victorian, Tasmanian, and South Australian winter. A 2–3mm boot works for 12–15°C water; 3–5mm for colder. Even outside of cold water, boots protect against sharp rocks, reef, and sea urchins on rock platforms. Look for boots with easy-open zippers so kids can manage them independently.