A wetsuit keeps your body warm by insulating the body heat with neoprene. When you are in the water, the water inside the wetsuit will be trapped and heated by your body temperature. The neoprene will not let the warm water go through and keeps it in the wetsuit. The thicker the neoprene, the better the insulation, the warmer the wetsuit.
When the wetsuit is still dry in and outside, you will be the warmest. When you go in the water the wetsuit also works as an insulation, but then with water outside and inside the wetsuit (see image below). The trapped water will slip out around leaking seams, holes, and head, arms, and legs gaps and will let warm water out and cold water in.
How much warmer does a wetsuit keep you?
A wetsuit is not a heating system that makes your body warmer, it is a way to keep your body at normal human temperature by insulating the body. So the body is warm and the wetsuit keeps it like that.
I think you could see it like this: a good (fitting) wetsuit should keep your body temperature around 37 degrees celsius. If the water is colder, you must need better insulation to keep the body warm. That’s why wetsuits have different thicknesses of neoprene. The thicker the wetsuit, the warmer the wetsuit, the better it will keep warm in colder water.
Yes, wearing some extra layers underneath your wetsuit keeps you warmer. Of course, it all depends on the material and thickness of that material. But overall every extra layer under your wetsuit helps with better insulation. But don’t forget every extra layer in the water will make you a lot heavier and will slow you down in the water. It will make movements in the water a lot harder and you will be exhausted.
What do you wear under a wetsuit to keep warmer?
There are some known types of clothes that are made to wear on the water or underneath a wetsuit. I will give some examples below, but if you are interested to see the entire list on what to wear: visit the blog about what to wear under a wetsuit.
- Lycra or Rashguard (T-shirt can also work)
I think this is the most common way of giving you extra warmth with an extra layer. There are different kind of lycras and rashguards, some from nylon and some from neoprene. The ones with neoprene have different thicknesses that can give even more warmth.
This is more of an extra wetsuit underneath your wetsuit. Can be a bit annoying but it gives the core body parts some extra warmth.
- Jumpsuit (for women)
It is more a special lycra for women, since I have never seen a guy wearing this :P. There is also a neoprene version of this jumpsuit.
Do loose wetsuits keep you warm?
No, loose wetsuits do not really keep you warm. It is probably better than not wearing a wetsuit at all (I am not really sure about that). But a wetsuit loses its function of insulating the warmth of your body when it is too loose around the body. So keep in mind a wetsuit should always be tight to have the best warmth performance.
How tight should a wetsuit be?
This question is always a bit difficult because a wetsuit should definitely be tight, but not too tight. A wetsuit is commonly described as a second skin so it should be as tight as a second skin ;). There are some guidelines for the right fit or tightness of a wetsuit. I will give some below, but if you want to know about the right fitting of a wetsuit, read the blog: how should a wetsuit fit?
A wetsuit should be too tight guidelines:
- Put your arms in the air
Putting your arms in the air when having the wetsuit on should give slight resistance. If too much resistance the wetsuit is too tight.
- Squat down and up
Squatting down and up should go easily. If not, the wetsuit is too tight.
- Check the lower back if there is a hole
There should be no gap between your back and the back of the wetsuit at the back. Because women have a more curved lower back, it is especially crucial to locate a tight wetsuit for that part of the body.