Why lap swimming changes the rules
Most swimwear built for a large bust is made for the beach: underwire, moulded cups, balconette shapes. In the pool that works against you. Underwire and rigid cups dig in on every push-off and ride up mid-set. What actually holds a bigger bust through a workout is compression — a suit that behaves like a sports bra: a wide racerback, firm straps, and true cup sizing (D–K), not S/M/L.
Fabric: what survives chlorine
If you swim more than twice a week, fabric matters more than style. 100% polyester or PBT (and blends like 94% polyester / 6% spandex) resist chlorine and hold their shape and colour for months. Nylon and elastane/Lycra feel softer when new but go slack and fade fast in a chlorinated pool. For daily swimmers, polyester isn’t optional.
The sizing problem — and how to solve it
Your bra size is a starting point, not the answer. Swim sizing runs differently from lingerie, and above a D the UK and US cup letters diverge (UK goes DD, E, F, FF, G…; US relabels the same cups). A Curvy Kate 30G, a Speedo 30, and a Funkita 12 can all fit the same body. Rather than guess, use the size finder below: enter your measurements once and it maps you to the right size in each brand.
What to look for — and avoid
- Look for: 100% polyester or PBT · racerback or cross-back · true cup sizing (D–K) · firm, wide straps · a fully lined front.
- Avoid: shelf bras and unlined cups · underwire if you swim laps · S/M/L-only sizing · pure nylon/Lycra if you’re in the pool often.
Brands worth knowing
Specialist bra-sized labels (Curvy Kate, Panache, Freya, Elomi, Bravissimo) go up to K–O cups but lean fashion and underwire — better for the beach than the lane. For real training, look at athletic ranges instead: Funkita’s support line, JunoActive’s AquaSport, Title Nine’s bra-sized sport tops, and Speedo’s cup-sized suits.
Compare
| Suit | At a glance | Sizes | Price | |
|---|---|---|---|---|
SP Speedo Speedo Endurance+ Solid Flyback Training One Piece, Cup Sized | Chlorine-resistantD–K cupflybackone piece | 34D,36D | $52 | Amazon→ |
SP Speedo Speedo Solid Super Pro LT Racerback One Piece, Cup Size F | Chlorine-resistantD–K cupracerbackone piece | 32C,34D,34E,36F | $68 | Amazon→ |
FU Funkita Funkita Racerback One Piece Cup Sized DD-G | Chlorine-resistantD–K cupracerbackone piece | 30DD,32E,34F,36G | $72 | Amazon→ |
FU Funkita Funkita Garden Glow Brace Me Back One Piece, Cup Sized DD-E | Chlorine-resistantD–K cupone piece | 10,12,14,16,18,20 | $75 | Amazon→ |
Prices and exchange rate as of Oct 27, 2026 (£1 = $1.3347). Allens prices are charged in pounds; the dollar figure is a conversion. Check the retailer for the current price.
Find your size
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FAQ
Can’t I just wear a sports bra under a regular swimsuit?
You can, but it drags, soaks up water, and stretches out quickly. A cup-sized suit is engineered to support when wet.
Is underwire ever okay for laps?
Rarely. It’s fine for water aerobics or casual swims, but for real sets it digs in on turns. Choose compression instead.
How often should I replace a training suit?
A chlorine-resistant polyester suit lasts many months of daily use. A nylon/Lycra one can go slack in weeks.