Start With Fit, Not the Number on the Label

Swimwear sizing is notoriously inconsistent. A size 20 in one range can fit like a 22 in another, and cup sizing often disappears entirely once you move past a certain point on the rail. This is why the label is a poor starting point and your own measurements are a far better one. Before you shop, take a soft tape measure and note four numbers: your underband (snug around the ribcage, directly under the bust), your full bust, your natural waist and your fullest hip measurement. Keep them in your phone.

When a top fits properly, the band should sit level all the way around and do the bulk of the supporting work — roughly eighty per cent of it. If you can slide more than two fingers easily beneath the band at the back, it is too loose; try a smaller back size with a larger cup. If it digs in or rides up, go the other way. This one adjustment solves more fit complaints than any other, and it is worth doing even if you have worn the same size for years.

Support Comes From Structure, Not Straps Alone

Straps are the least reliable source of support in any swimsuit, and thin halter ties are the worst offenders. Look instead for the internal engineering that holds everything in place without you having to think about it.

• Underwired cups — a proper underwire, encased in soft casing, separates the bust and stops the uniboob effect that moulded, non-wired tops often create.
• Seamed or moulded cups — seams give a natural, lifted shape; moulded cups give a smoother line. Both beat an unlined shelf bra.
• Adjustable straps — look for metal or sturdy plastic sliders rather than fixed elastic, so you can shorten the straps for a firmer lift.
• Power mesh wings and side boning — these smooth the back and sides and stop the band from rolling down when you move.
• A hook-and-eye fastening — far more adjustable than a pull-on band, and it lets you loosen the fit after a long day in the sun.

If you prefer a non-wired style, seek out a wide, deep underband and a concealed elastic support panel. These hold surprisingly well and suit anyone who finds underwires uncomfortable in the heat.

Bottoms That Stay Put

Bottoms are where many people give up, usually after one too many pairs that roll down at the waist or creep up at the leg. The fix is in the construction. A high-waisted brief with a wide, doubled waistband will sit comfortably at or just above the natural waist and stay there. Ruched side panels are a clever detail: the gathers allow the fabric to stretch over the hip and tummy without pulling the whole garment out of shape.

Check the leg line too. A high-leg cut with a modest front gives longer-looking legs, while a full brief with a higher back offers more coverage if you are conscious of your bottom. Silicone gripper tape along the top edge of the waistband is a small feature that makes a genuine difference, especially if you plan to swim rather than just sunbathe. And always squat, bend and sit in the fitting room — if a bottom shifts during a squat, it will shift in the sea.

Silhouettes That Offer Coverage With Confidence

You do not have to choose between full coverage and a flattering shape. Several silhouettes deliver both.

• Tankinis — the two-piece convenience of a bikini with the coverage of a swimsuit. Choose a top with a firm underband and a hem that overlaps the bottoms by a good few centimetres so no gap appears when you raise your arms.
• Swim dresses — a fitted bodice with a gently flared skirt that skims the hips and thighs. Look for a skirt that finishes mid-thigh for ease of movement.
• Wrap and ruched fronts — the diagonal drape creates a waistline and disguises the tummy area without adding bulk.
• Blouson and A-line swimsuits — loose through the middle, fitted at the bust and hip, so the eye reads a defined shape rather than a tent.

Whatever you choose, check that the armhole does not gape when you reach forward and that the neckline stays flat when you lean over.

Fabric, Lining and the Details Worth Checking

Look for a fabric with a decent elastane content — around twenty per cent is a good benchmark for recovery, meaning the suit springs back into shape rather than stretching out after an hour in the water. If you swim regularly in a chlorinated pool, choose a chlorine-resistant fabric; standard elastane will degrade quickly otherwise. Double lining across the front adds opacity when wet and provides a smoother finish.

Removable padding is useful because you can adjust the level of shaping to suit the day, but check that the pads sit in sewn-in pockets rather than floating loose. UPF 50+ fabric is a sensible extra if you burn easily. Finally, rinse your swimwear in cool water after every wear and dry it flat in the shade — this alone can double its useful life.

Making the Decision and Feeling Good in It

Order two sizes where you can, and check the returns policy before you buy. Try your options on at home, in daylight, and walk around for ten minutes rather than judging from a two-second glance in a mirror. Notice how the garment feels when you sit, bend and reach — comfort is the most reliable indicator of a good fit.

Confidence does not come from covering up or from squeezing into something that hurts. It comes from wearing something that stays where you put it, supports you properly and lets you forget about it entirely. That is the real test of a swimsuit, and it is one you deserve to pass.