Diving in the Tropics: Is staying warm really an issue?

By Gary Ward

We all imagine diving in the tranquil blue warm waters of the tropics.  We can see the waves gently lapping against the side of the dive boat and the azure blue patches in the water.  The sun is shining and there are fluffy white clouds drifting in the sky. The water temperature is a heady 29 degrees centigrade (84f) and there is a gentle breeze coming off the island…  Is it possible that in these waters’ divers could possibly get into trouble with extreme cold?  Today we look at how in these seemingly idyllic conditions divers can experience extreme cold and hypothermia

The human body has a core temperature of 36.5-37.5 degrees centigrade (97.7-99.5f).  This normal temperature range is referred to as normothermia.  Our temperature is maintained through a process of thermo-regulation, which is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different.  Our thermo-regulatory systems differ from person to person, but also dependent on the activity we’re doing.  When we’re active we generate heat and our bodies try to dissipate this heat away from our core.  When we’re inactive some of us will feel cold, particularly in our extremities.

We’re also aware through out introductory SCUBA lessons that water conducts heat away from the human body twenty times more aggressively than air, which is why we can feel hot in 29-degree air but may find 29-degree water chilly.  Mathematically we can look at a formula for energy (joules) lost to water per cm2 of exposed skin per degree change in temperature, which looks something like this:

So, if a diver was wearing little or no exposure protection in tropical water their core body temperature would be potentially 10 degrees centigrade (50f) higher than the ambient temperature, with their body required to work 20 time harder to maintain that core.  If we were gently diving and lowering our metabolic rate to relax into the diving its easy to see why some divers might struggle to stay warm.  The danger we might face is that if our core temperature drops more than 1-2 degrees centigrade (1.8-3.6f), then this could induce hypothermia, a serious condition where our thermo-regulatory system struggles to maintain core body temperature.

It can seem bizarre as you take a cooling dip in the ocean on your session on the beach in your bikini or swim-shorts that prolonged exposure for some through diving could result in hypothermia?

As divers in the tropics though, we’ve become very familiar with this phenomenon and promote a system of layering with relatively thin exposure suits to ensure divers remain comfortably warm.  An exposure suit works by having a layer of fabric filled with air pockets close the skin.  This fabric allows a small volume of water to pass through it which our body then warms (through conduction).  The heat is not able to conduct through the fabric easily as the heat needs to transfer through the air pockets and as long as the water trapped inside does not flush out too easily, we’ll stay warmer.  For many we would start with a 2-3mm shortie wetsuit, which on the whole is a good option for tropical exposure protection.  The shorty is made from closed cell neoprene, which is an excellent material for heat retention. 

However, if this is insufficient, we would recommend layering up with something like a ‘Hyperflex’ base layer.  Hyperflex base layers are made from 1.5mm Atomic Foam, which is a super stretch neoprene infused with a higher count of air cells and achieves a higher insulation rating than standard neoprene for the same thickness and weight.  These tight-fitting tops, like the ones sold here in our shop, are tight fitting and help to hold a lower volume of water close to the skin which also does not easily flush.  In doing so it significantly reduces the conduction effect of the water on the body and retains a significantly higher proportion of your body heat.

For divers with a little more “Bio-prene” on them (natural air and cell layers under the skin), then many find that a Hyperflex type top and board shorts are enough exposure protection and do not then need a wetsuit at all.

In summary, even in warm tropical waters the body loses heat very rapidly in the water which necessitates the need for exposure protection.  Layering with a combination of thin tropical shorty style wetsuits and Hyperflex type base layers is the best way to maintain a comfortable temperature when diving and being comfortable in the water when diving makes for a much more enjoyable dive….

If you have any questions about tropical exposure protection or are interested in our range of Deefer Diving Hyperflex tops, please contact us through www.deeferdiving.com