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Staying Warm Whilst Coldwater Diving

By: Thomas Muller - Updated: 25 May 2012 | comments*Discuss
Diving Cold Water Hypothermia Drysuits

Being cold while diving is not only unpleasant it’s exhausting and potentially dangerous. By employing specialist clothing and a few common sense tips, there is no reason to ever dive cold.

What is Cold Water?

To prepare for cold water, it would be useful to know when warm water becomes cold water and when cold water becomes extreme cold. However, it is difficult to make clear distinctions between levels of cold because it is largely dependent on a person's body, experience and clothing.

Generally speaking temperatures between 20°C and 7°C constitute cold water and would necessitate wetsuits towards the top of the range and drysuits towards the bottom. When the temperature drops between 7°C and 4°C even drysuits may struggle keeping you warm, and it is here the base layers become crucial.

Hypothermia Risk

Besides feeling uncomfortable and reduced body dexterity, the big risk underdressed divers face is hypothermia. This condition occurs when the body’s core temperature falls below 35°C, at which point it starts to malfunction.

Recognising Hypothermia Symptoms

Unfortunately it can be difficult recognising a body temperature drop. First signs of hypothermia may include cold hands and feet, and loss of dexterity and grip strength. A sufferer may experience difficulties performing routine tasks, states of confusion or a tendency to repeat duties. They may also experience feelings of chilliness followed by sporadic shivering.

If a diver suffers from any of these symptoms then the dive should be brought to a swift conclusion. Also, as it is particularly difficult to judge your own thermal condition, it is important to note any behavioural changes in your diving partner.

Cold Water Protection

A diver exposed to cold water or even reasonably warm water for long periods must wear protective clothing. A variety of diving suits are available, ranging from standard foamed neoprene wetsuits and drysuits to specially heated suits, as well as insulating base layers, hoods, gloves and socks.

The level of insulation and wet and dry suit thickness required not only depends on the temperature of the water but also on an individual’s sensitivity to cold. Children and older divers often require greater thickness, while overweight divers require less because of their natural insulation.

Wet and Dry Suit Fitting

To ensure both warmth and dexterity, a diving suit needs to fit properly. If it doesn’t then it will leak. It should feel like it’s moulded onto your body and glued to your skin, so that it moves when you move.

Additionally, the length, shoe size and wrist and neck seals must all be exact in order to eliminate any water trickling in and to ensure the best insulation. It’s also important also to bear in mind that diving suits do wear out, sometimes imperceptibly. The typical life span is between 3 and 5 years.

Insulation Beneath the Suit

In colder waters where a drysuit is required, a crucial factor in staying warm is the clothing worn beneath the suit. By choosing base layers carefully you can maintain great flexibility in the coldest of conditions.

The base, moisture-wicking, layer is that closest to the skin. This should remove moisture from the body and be lightweight synthetic or silk long underwear. It should fit relatively snugly against the skin without being too restrictive.

Between the base layer and the suits is the insulating layer. The number of layers depends of the degree of insulation required and is the critical difference between diving in cold water and extreme cold water. The function of the insulating layers is to trap body heat while enabling perspiration to escape. Feet also require an insulating layer using either fleece or wool socks.


Regardless of how warm your body is under water, if your hands are not adequately protected it will undermine the whole body protection and result in significant discomfort and even danger, as dexterity will be hampered by the cold.


Keeping the head warm in cold water is also key concern. Even though they might feel uncomfortable, restrictive and even claustrophobic, a hood is essential. Neoprene hoods come in different thicknesses - typically 3, 5 and 7mm - but although the thicker they are the warmer they are, they can also become increasingly uncomfortable. It is important to get a good snug fit to minimise any water flow and it should also cover as much of the head as possible without affecting diving equipment.

Importance of Re-warmingAs part of keeping warm, it is crucial that at the end of a dive a cold diver is re-warmed. This is best accomplished by consuming hot liquids such as soup or coffee, drying off in a warm place, and bathing in warm water. The diver should then change into warm, dry clothing and follow up with some mild exercise to improve heat production and circulation.

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