I watched the poor bugga emerge from the water in Bali. He was wearing a 5mm wetsuit and had been dripping with sweat while on the dive. His face and neck were a deep red color. I watched in amazement as he struggled to remove his rubber skins on the beach, exhausted from the short dive in the warm 29c ocean.
A diver must consider the thickness of a wetsuit when purchasing. A wetsuit of incorrect thickness can cause a diver to shiver or make a wetsuit difficult to put on and take off. The industry refers to the number on the front of a wetsuit as small. The number is measured in millimeters and seems to mean so little. But to a diver, that small number can mean so much. The number can mean how warm a diver will be, how much movement a diver will have in the wetsuit and how a dive will affect a diver in terms of fatigue.
What the numbers actually mean
Many people only consider the warmth of a wetsuit when determining the thickness of a wetsuit. But another very important factor is the amount of water that gets stuck between the wetsuit and your skin. This water is then heated up by your body, creating extra insulation. However, the water stuck between your wetsuit and your skin also provides extra resistance, increases your buoyancy, and causes fatigue as your muscles have to work harder to do the same amount of work as you would with thinner wetsuits.
When selecting a wetsuit there are 4 things to take into consideration for selecting the appropriate thickness: The temperature of the water that you will be diving in, The activity that you will be doing in the water, The duration that you will be in the water and Your personal tolerance to cold.
- The water temperature where you’ll actually be diving or surfing, not where you wish you were going
- How long you typically stay in the water per session
- Your personal cold tolerance (some people run warm; others are reaching for a jumper in summer)
- What activity you’re doing, since freediving and surfing have very different flexibility demands
Below is a guide for what thickness wetsuit to use for various scenarios including the good points and some of the points where the wetsuit will fail.
The 5mm: serious warmth, serious commitment
The first suit thickness to consider is 5mm. The 5mm wetsuit is serious warmth for serious divers. It is not recommended for average fitness people, as the thickness of the suit requires considerable strength to put on and take off, and to use for dives. These suits are very buoyant, and are best suited for deep freediving or very cold spearfishing. Below 18°C — and especially anywhere near 12 to 15°C — a 5mm wetsuit stops being an option and starts being a requirement. The 5mm wetsuit will keep you warm in cold water, but the suit will also make your dives very
If you are to be diving in water below 18 degrees Celsius then you are going to need 5mm plus of neoprene for serious warmth. The cold water will now be a serious factor for the divers ability to complete a dive safely and with minimal cold tolerance discomfort. However as we have seen above a 5mm wetsuit has a number of drawbacks including; high buoyancy, low flexibility and can make it very difficult to enter the water in a hurry if needed. The warmth that a 5mm wetsuit will provide for the diver in cold water is a major factor, and may even be the deciding factor for some divers as to whether they are able to complete a dive safely. Stay warm, it is the most important aspect of your dive in cold water.
Even if you dive in warmish water there will come a point at which you need serious warmth. At 18°C and below 5mm wetsuits are seriously the only game in town for warm and the buoyancy of thick wetsuits has to be fought by freedivers and the additional resistance from the suit to every kick and every arm pull at the surface and on the dive will have worn you out by the time you get to the bottom of your dive.
The 3mm: the one most people should probably own
The 3mm is the best “all-around” suit for most divers and will extend your time in the water by hours over thinner wetsuits. For example, in 20-22°C water a good 3mm wetsuit will allow you to stay in the water for 2-3 hours or more. This makes the 3mm the perfect wetsuit for Freedivers, Spearfishers and general divers that require lots of flexibility. The 3mm is the perfect “all-around” suit for most all-around divers and will be used in a wide variety of conditions.
A 3mm wetsuit is also the ideal wetsuit for spearfisherman who require to move around in the water freely. Although every individual is different and can have their own different experiences with wetsuits, generally speaking a 3mm wetsuit will allow the wearer to stay underwater for longer periods of time than a 5mm thick wetsuit of equal quality. When shopping for spearfishing wetsuits, make sure to look at the 3mm open-cell options as they have the best stretch of any neoprene wetsuit on the market.
1.5mm suits: thin warm suits for warm waters
Thin wetsuits are made of 1.5mm neoprene, and are almost too thin to consider as an option for most people however they have found an awesome niche in the market place and are perfect for warm tropical waters (Above 26 Degrees C). Thin wetsuits offer the diver, spear fisher or even the occasional snorkeler lots of benefits including, lots of flexibility and movement while in the water, great for Freedivers, protection from the sun as well as any reef or jellyfish stings etc while allowing for good movement and flexibility. The only down fall of these type of suits is their warmth properties and their ability to last for long extended periods of time while in the water above 26 Degrees C, however for short periods of time, such as for Freediving or for Snorkelers doing lots of short dives these suits are the perfect option, as well as for people who like to do occasional ocean swims in tropical waters. For people that do extended ocean swims in tropical waters however, we would recommend going to recommend a pair of Board Shorts or a Lycra Suit as these type of suits will last longer and provide more comfort than a thin wetsuit.
It is also important to remember that the amount of time you can wear to use a 1.5mm wetsuit during the day even in warm tropical waters will decrease as the period of time increases. So after about 1 1/2 to 2 hours the wetsuit will start to feel cool. As you descend to greater depths the water temperature will also start to decrease rapidly and the wetsuit will have little to no warmth.
| Thickness | Best water temp | Flexibility | Buoyancy effect |
| 1.5mm | 26°C and above | Excellent | Minimal |
| 3mm | 18°C to 26°C | Good | Moderate |
| 5mm | 12°C to 18°C | Reduced | Significant |
How Cold Tolerant Are You?
We’ve all seen two people of roughly the same size in the water at a temperature of around 20 degrees Celsius. One of them is happily swimming about, freediving every now and then and generally seems to be having the time of his life. The other is shivering, his teeth are chattering and he’s getting out of the water after only 30 minutes. They’re both at the same temperature, so what’s going on here? Why is one of them comfortable and the other in agony? The answer is simple: they’re losing heat at different rates. Their body composition, circulation, age and level of fitness all play a huge role in how fast they shed heat and this is something that they can’t control. All they can do is try to find a wetsuit that helps them to stay warm for as long as possible.
It’s also important to note when purchasing a wetsuit that the suits are sized to fit for average divers and those who do not ‘run cold’. If you are one of these people then it is always best to Size up in the Thickness to keep the cold out. The extra thickness of a 5mm suit in cooler conditions will see you dive for hours in comfort. A 3mm that is too small for you will see you losing warmth to the water with each stroke of your arm and kick of your leg. There is no shame in wearing more neoprene than the next person, only that you are more sensible to your needs then they are.
Fit. It Matters.
A baggy 5mm wetsuit will mean that lots of cold water is going to penetrate to your skin as you move around. This type of wetsuit loses heaps of thermal value in all directions as you go about your activities. A well fitting 3mm wetsuit will give you heaps more warmth than a sloppy fitting 5mm wetsuit in just about all situations. Try on as many wetsuits as you can before you make a purchase. Your life on the beach will be far better for it if you have a good wetsuit that has been purchased after trying on several on, as opposed to buying online after reading specs of various different wetsuits. A wetsuit is just a piece of neoprene, and a number on a label is just a number on a label. What that number does on your body is what counts!
