Tomos Llewellyn
Why bother with fins at all?
If you swim outdoors in Britain, you already know the water rarely gives you anything for free. A river fed by a chalk spring sits at around ten or eleven degrees Celsius all year, and the same goes for many of the old well pools and plunge spots that have drawn people for centuries. Fins — short swimming fins, not diving fins — are one of the simplest ways to make that water feel more manageable. They add a gentle push to every kick, so you can hold a steady line, keep your face out of the chop when you need to, and cover ground without thrashing.
They are also a teaching tool. Fins exaggerate what your ankles and hips are doing, so you feel straight away when you are kicking from the knee instead of the hip. For anyone building confidence in open water, that feedback is worth more than raw speed.
Short and flexible wins in open water
The fins that suit a pool length or a tropical snorkelling trip are not the ones you want. Long blades are heavy, awkward to walk in, and they load the ankle with every kick. In a cold UK river or a choppy sea pool, that quickly becomes tiring and, with a stiff pair, painful.
Look for a blade roughly 20 to 30 centimetres long, made from soft rubber or a flexible silicone blend. A short blade lets you keep a natural flutter kick — small, quick, driven from the hip — rather than the slow, sweeping stroke that long fins demand. Flexibility matters as much as length: press the blade against your forearm and it should bend easily, without a fight.
- Short blades for flutter kick and general open water swimming.
- Soft, flexible materials so your ankles are not fighting the fin.
- Light weight so you can carry them in a bag and walk a few metres without wobbling.
- A drainage channel or vent if you can find one, which stops water pooling and dragging.
Getting the fit right
Fit is where most people go wrong. A fin should feel snug across the top of the foot and around the heel, with no single pressure point. Your toes should be able to move, but not slide forward and back. If the fin shifts when you kick, you will get rubs — and a rub in cold water, several hundred metres from the car, is a miserable thing.
Always try fins on with the socks or boots you intend to wear. A foot pocket that feels perfect in a warm room can become a vice once you add a three-millimetre neoprene sock, or feel loose once the neoprene compresses. Do not size up hoping to grow into them. A slightly snug fin that softens in the water is better than a loose one that flaps and wastes your effort.
Cold water, boots and foot pockets
British springs and wells are cold year-round, and cold feet lose feeling fast. Neoprene socks or thin boots are not optional for most swimmers, and they change how fins fit. Open-heel fins with an adjustable strap are generally easier here, because you can wear them over a boot and tighten them down. Full-foot fins are simpler and give a closer feel, but you will need to match the pocket size to your sock.
One thing to know: finning pushes cold water past your feet, so they can chill faster than you expect. If your feet go numb, you lose the fine control that makes short fins useful. Keep sessions short at first, and get out while you can still feel the ground beneath you.
Technique first, power second
Wear fins for ten or fifteen minutes, not an hour. Start with a relaxed flutter from the hips, ankles loose, knees barely bending. The fin does the work; you just steer. Resist the urge to kick hard — big, powerful kicks are what strain ankles and calves, especially in stiff fins or on a cold day when your joints are not warmed up.
If you are used to breaststroke, either take the fins off or use a very gentle whip kick with a narrow recovery. The wide, snapping kick that works without fins can twist a knee once a blade is attached.
Where to test and how to build up
Start somewhere forgiving: a lido, a sheltered sea pool, a calm stretch of a spring-fed river, or a well-known wild swimming spot with an easy entry. Practise finning on your front and on your back, and get used to taking them off in the water — you may want to do that before you climb out onto slippery stone.
Build up slowly. Add five minutes each session, and finish before your feet go completely numb. Rinse them in fresh water, dry them out of direct sun, and store them flat rather than crushed under a bag. Looked after, a good pair of short fins will last years and quietly transform how comfortable you feel in cold, open water.
