I recently watched a diver surface from a 45 minute reef dive only to shake so hard that he could only slowly unclip his BCD from his tank. His wetsuit looked ok when he first put it on – probably even the right thickness for the cold water – but as he pulled off his Hood and Gloves on the surface it became apparent that the wetsuit was half a size too wide around the chest. Therefore the whole suit had filled with cold water for the entire 45 minute dive. He was finally back on the rack, cold and clearly annoyed, only 20 minutes or so into the day and after having cut his 1 hour dive short.
I know this can be fixed with better equipment, but in my experience the majority of these sorts of problems are due to simple things that can be fixed with a few minutes of trying on gear in a changing room before the dive. A wasted dive with a cold and frustrated diver could be prevented by ensuring that all of your gear fits correctly.
The flushing problem nobody talks about enough
I wish more people understood that wetsuits do not keep you warm by stopping water from entering the suit. What wetsuits do is trap a layer of water between your skin and the suit. This layer of water is then heated by your body. The wetsuit then holds this warmed layer of water against your skin keeping you warm for as long as possible. However once this layer starts to ‘flush’ or move, cold water then enters the space between your skin and the wetsuit causing you to lose warmth with every kick of your fin.
The primary areas of failure of a wetsuit are the neck, wrists and ankles. A diver is in constant motion whilst underwater. Therefore, there is always movement of the suit around these areas which in turn causes water to flush through the suit. As a result, any leakage at entry points to the suit will cause problems immediately. On a long dive, i.e. a 45 minute reef dive, what may seem like adequate wrapping of neoprene around these areas on the surface, in actual fact can cause severe problems once in the water.
It is very important to choose a wetsuit of correct size, as a wetsuit that fits well and doesn’t leak will keep you warmer for longer than a wetsuit of same specification that fits poorly. A wetsuit is designed to trap a layer of water next to your skin and as your body heats up this layer of water, you are then left with a layer of warm water between you and the outside of the wetsuit. If this layer of warm water is constantly being flushed and diluting with cold water then your body must work harder to try and warm the water back up to keep itself warm. This in turn can cause excessive fatigue during longer dives.
Long Dive Features
When choosing a diving wetsuit for longer dives, one needs to consider how a problem will affect you over time. A slow leak in a 20min splash is not a problem, but it can fill a bucket on a longer dive. This is why it is best to consider the features of a wetsuit in terms of how they will hold up over time. Will your suit stay in place over time, will it allow for the movement required for your dives, and will your suit handle the increase in pressure over time. As a result, flat stitching vs sealed stitching with a wetsuit is going to be a major point of difference when comparing a cheap suit with flat stitched seams to a mid priced suit with sealed stitching.
- Thermal insulation rating: Match your wetsuit’s thickness to your water temperature honestly, not optimistically. A 3mm suit in 18°C water on a 30-minute dive is fine. On a 70-minute dive, you’ll be counting the seconds until ascent.
- Flexibility in the shoulders and arms: Stiff neoprene causes fatigue over long sessions. If you’re fighting your own suit to complete each kick cycle, you’re burning energy you genuinely cannot afford to burn.
- Reinforced knees: If you’re doing any reef or wreck diving where your knees occasionally graze surfaces, bare neoprene degrades surprisingly fast. Reinforced panels extend the suit’s useful life considerably.
- Flatlock vs. blind stitched seams: Flatlock stitching is fine for warmer water, but if you’re diving anything below about 20°C, blind stitching — and ideally glued seams — makes a real difference in water intrusion over the course of a long dive.
When buying online for diving wetsuits for cooler water diving the best indicator of a good quality wetsuit would be the construction details of the wetsuit as opposed to the outward appearance of the wetsuit. Although a wetsuit may look great and you can purchase the wetsuit at an affordable price as opposed to other similar models on the market the actual performance of the wetsuit would more than likely be poor, especially in cooler water with flatlock seams. A mid-range wetsuit with sealed stitching would perform much better in similar conditions.
Suit Features for Different Dive Lengths
| Feature | Short dives (under 30 min) | Longer dives (45+ min) |
| Seam construction | Flatlock acceptable | Blind stitch or glued essential |
| Fit at neck and wrists | Minor looseness tolerable | Tight seals critical |
| Neoprene thickness | Can often go thinner | Err toward thicker |
| Knee reinforcement | Optional | Strongly recommended |
| Flexibility rating | Less critical | High flexibility reduces fatigue |
Sizing: try it like you mean it
This is an area that is commonly overlooked by potential wetsuit buyers. Many people simply stand upright in a changing room, take some wrist and height measurements and say that the wetsuit fits ‘perfectly’. Then off they go for their dive, doing arm over heads with their BCD and before long a huge gap has opened up at the lower back of the wetsuit, often the size of a letterbox. This is because trying on a wetsuit for diving is a lot different to how you stand upright in a changing room. You must move around a lot more and pay particular attention to how the wetsuit fits up over the neck and whether the wetsuit restricts breathing when doing deep inspirations into the wetsuit.
Check that you can flex your arms over your head while wearing your wetsuit and also sit in a squatting position. Also test the flexibility of your wetsuit around your waist to check for gaps. Test the seal around your neck also by twisting your waist to see if there are any leaks. Also when putting your wetsuit on make sure that it’s not to tight around your chest so that it doesn’t restrict your breathing when you inhale fully. As you breathe in fully with tight wetsuit across your chest you will start to breathe shallow.
So to sum up the issue of wetsuits and air space between wetsuit and skin: the wetsuit needs to fit over the whole body like a second skin, and any air space will reduce thermal retention dramatically. It is also very important to check a wetsuit out for flexibility while it’s still on the surface. If you are flexing your arms up over your head while wearing a wetsuit then this should be very easy to do, as well as squatting down and then coming back up to standing. If for example the neck of the wetsuit is way to tight around your neck then inhaling while wearing it on land will be very difficult, also.
Flexibility.
A major shift has occurred in neoprene flexibility over recent years allowing for very warm suits that are also extremely flexible for the diver. For those who are choosing between two identical thickness suits, look for increased flexibility in shoulder movement for the longer dive as this will enable greater comfort for the diver allowing them to have more energy for the rest of the dive rather than being fatigued from a suit that works against the diver’s natural movement.
Fatigue will also play a huge part in how your body reacts to your wetsuit during a dive. Don’t allow your gear to be another fight for your body during the dive. It already has to fight for your air supply and buoyancy, don’t make it any harder.
None of this matters much if you don’t get the basic element of sizing right. The best wetsuit in the world, with the smartest stitching and design for maximum flexibility will be of no use to you if cold water keeps flushing through loose seals for the whole dive.
Buy the wetsuit for the dive that you are planning – the long dive, not the short dive!
