Published 15 September 2026
It's the part that rubs, it's the reason a lot of children won't keep them on, and enough parents cut it out that there are guides explaining how.
Turn a pair of swim shorts inside out and you'll usually find a second layer sewn in at the waistband: a light nylon mesh, shaped like briefs, attached at the top and hanging free at the leg.
It is not a lining in the sense of a smooth inner layer. It's an open weave with a cut-and-overlocked edge that sits directly against the thigh — and on a child running, climbing and sitting down in sand all day, that edge is the thing doing the damage.
"He has chafing issues in most clothes, but swim trunks are the worst culprit." A parent, in a public review of a children's swim short
The honest answer is inheritance rather than intent.
Mesh liners came from adult men's swim shorts, where they do two jobs: some support, and opacity in a garment cut from thin woven fabric that goes see-through when wet. Both are real reasons on that garment.
Children's swim shorts were then designed as scaled-down versions of the adult ones, and the liner came along with the pattern. On a child's garment neither original reason holds up especially well:
So it persists mostly because it has always been there, and because removing a component means re-patterning a garment that currently sells fine.
The mesh makes a pocket that sand gets into and does not easily come out of. Sand against wet skin, held in place by fabric, is the mechanism behind most beach-day soreness.
Two layers hold more water than one. A child who is in and out of the sea all day spends that day in the wettest part of the garment.
The leg openings of the liner fall at the upper inner thigh. That is the highest-friction area on a moving child, and it is where an overlocked edge does the most harm.
Two layers to line up, wet, on a child who wants to be back in the water. A small thing that happens several times a day.
Plenty of people do, and the shorts do not fall apart — the liner is usually attached only at the waistband seam.
The cut edge will be raw. It sits inside the waistband where it does not touch skin, and swim fabric does not fray the way a woven does, so it is usually fine left as it is.
It voids any returns, obviously. And it is worth saying plainly: you should not have to do surgery on a new garment. That people do is the interesting fact here.
If you are buying rather than modifying:
| Look for | Why |
|---|---|
| Single-layer knitted fabric | Nothing inside to rub, and it dries at one speed |
| A close cut, not a loose one | A loose short slides against skin; a fitted one moves with the leg. Same principle as cycling shorts |
| Flat or covered seams | Bulky seams at the inner thigh cause the same problem the liner does |
| No drawcord | Knots when wet, and a hard toggle presses in when a child lies down |
| Fabric weight around 190–220 gsm | Heavy enough to be opaque, light enough to dry fast |
Swimming costumes and swim leggings already work this way, which is a reasonable check on the logic: nobody puts a mesh liner in a child's swimming costume, and nobody misses it.
We are making children's swim shorts with no liner, no mesh and no gusset — one soft layer, a close cut and low-profile seams. The comfort comes from what is absent, not from adding length or padding.
We are not launching until 2027 and there is nothing to buy yet. If the liner is the reason you are reading this, the most useful thing on this page is probably the section above about what to look for — that advice works whoever you buy from.
There's a list if you want to know when ours exist. And if you have cut a liner out yourself, we would genuinely like to hear about it: hello@wildedays.com.
What colour swimwear can you actually see under water? — we modelled eight prints at depth. Blue, the most common colour in children's swimwear, turned out to be close to invisible.