Buying a wetsuit for Irish water: what thickness you actually need

The single most common mistake we see is somebody buying a suit that would be perfect in Portugal and wearing it in Clare. The second is buying one a size too big because it was easier to get on in the shop.

Swimming and diving are not the same problem

This is the bit people get wrong, and it is not about toughness. A swimmer is working hard and generating heat the whole time. A diver is close to motionless for forty minutes, often deeper and always colder. The same water needs a completely different suit depending on what you are doing in it.

• Swimming in Kilkee: 3 mm is the minimum. Plenty of regulars wear 5/4 outside high summer.

• Diving in Kilkee: 7 mm, or a drysuit. A 3 mm suit will not do, no matter how hardy you are.

What the numbers mean

The figures are neoprene thickness in millimetres. Where you see two numbers — 5/4, 4/3 — the first is the thickness over your core and the second is over your arms and legs. Thicker where you lose heat, thinner where you need to bend.

Two features matter more than most people realise. A sealed or taped suit keeps far more warmth than a flatlock-stitched one, because plain stitching lets water through the seams. And the entry system — back zip, chest zip or zip-free — changes how much water flushes in: back zips are easiest to get into and the coldest of the three.

When a drysuit is the honest answer

If you intend to dive here through the winter, or you do long dives, or you simply feel the cold, a drysuit changes your season more than any other single purchase. It keeps you out of the water rather than warming the water against you, and you can put layers underneath to suit the day.

Two honest caveats. It costs considerably more, and it needs training — a drysuit changes your buoyancy and how you manage it, which is exactly why the dry suit speciality exists. Do not buy one and take it straight into open water without instruction.

A suit that is slightly too tight will warm up. A suit that is slightly too loose will never be warm.

How to tell if it fits

A wetsuit works by trapping a thin layer of water against your skin and letting your body heat it. Loose suit, and that water keeps being flushed out and replaced with cold — which is why an oversized suit is worse than no suit at all for warmth.

• It should feel snug to the point of being slightly annoying on land. That is correct.

• No loose pockets or wrinkles at the lower back, behind the knees or under the arms — those are where the cold water sits.

• You should be able to reach both arms across your chest and squat down without it fighting you.

• It should not restrict your breathing or pull at your neck. Snug is right, throttled is not.

The extremities matter more than the suit

Most people who say they are cold are actually saying their hands and feet are cold, and they stop enjoying it long before their core is in any difficulty. Boots and gloves are cheap next to a suit and they extend your season by months. A hood does more for warmth per euro than almost anything, because you lose a lot of heat through your head in cold water.

Buy it now, not in May

The shop on the pier has its end-of-season deals on — suits, boots, gloves and accessories. Buying at the end of a season rather than the start of the next one is straightforwardly cheaper, and it means you own the thing for the best diving weeks of the year rather than after them.

Come in and try suits on rather than ordering by size chart. Fit varies enormously between brands, and the difference between a suit that fits and one that nearly fits is the difference between a good winter and a suit hanging in the garage. We are on the East Pier, or ring 085 255 2064.