Undersuit temperature guide

Remember that these are only guides as there are so many variables involved but if you would like to get some further advice and help buying an undersuit please contact us!

These suggestions are based more for membrane or trilaminate drysuits, you can adjust slightly on the thinner or cooler side for a neoprene suit.


20 Degrees Celsius +

You are going to be nice and toasty down there in your drysuit so you’ll probably only going to need a base layer to wick the moisture away from your skin. Here are some options:

  • Fourth Element J2 Base Layer in both Mens and Ladies
  • Waterproof BodyTec Single Unisex Top and Bottoms


15-20 Degrees Celsius

Average summer UK sea temperature range so just a little nippy perhaps towards the end of the dive. A good base layer will help to keep your skin comfortable and dry whilst a thin thermal layer should give you ample protection against the cold. If you feel cold quickly you can always go for a slightly thicker thermal layer.

Base Layers

  • See above for Base Layers

Thermal Layers


10-15 Degrees Celsius

Things are getting colder now so you’ll need to choose a thicker thermal layer. Your trusty base layer will continue to do its job, leaving the thermal layer to do all the work of helping to keep you warm. As an upgrade if you feel the cold you could swap the base layer for a thin thermal layer but make sure the material has good wicking properties.

Base Layers

  • See above for Base Layers

Thermal Layers


5-10 Degrees Celsius

We are into winter UK sea temperatures here. You are almost certainly going to need two thermal layers, a thinner one (like the Fourth Element Xerotherm) to act as your base layer and a thicker layer for warmth. If you are nearing the bottom on this temperature range you might also want to consider an extra layer over your body core to help keep your temperature up.

As well as the thicker and dual layer options we mentioned above you might want to consider something a little more advanced like the Fourth Element Arctic Expedition which uses varying layers, materials and thicknesses in different regions of the body to offer the best insulation solutions. Fourth Element call this Biomapping and it is a result of lengthy research into body heat loss.


1-5 Degrees Celsius

Layer, layer, layer ….. literally. Plenty of thermal layers needed here. A good thermal base layer, thick middle layer and perhaps something extra over your core such as a Waterproof 3D Mesh Vest which maintains insulating air gap using anti-compression materials. You can use pretty much any combination of different garment types and thicknesses we have mentioned before to achieve something that works for you.

If you feel the cold you might want to look into something a bit more specialised that take advantage of some pretty interesting materials and designs. The Fourth Element Halo 3D uses a combination of different thicknesses and layers across different regions of the body to create an advanced full undersuit. On top of that it uses anti-compression materials to maintain the insulating air gaps around your core and makes you look pretty awesome too.


1 Degrees Celsius and... Below?!

You need some serious thermal kit from this point on. You might want to consider heated options such as the Thermalution heated vests in addition to the best thermal layers you can get your hands on

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