It wasn't so long ago that the onset of winter meant it was time for your diving equipment to undergo its 'end of season maintenance'. At about the same time that Blue Peter presenters stuffed their tortoise into a cardboard box (remember children, leave holes for it to breathe), so too it was time to hang up your fins. Yes, there were winter dives, but on the whole these were 20-minute dips into sheer freezing hell. You didn't need run times - you just used the symptoms of hypothermia to calculate your bottom time before bolting from the water and trying to control the shivering long enough for you to twist off the brass fastenings on your wetsuit top. Not for us were the numerous hours spent idly watching television.
But enough of this 'when we were real divers' nonsense, today diving is a year round activity. Winter is the time when a great deal of training takes place and the cold is just another equation to be factored into the dive plan. Yet many people still find diving through the winter an excruciating experience.

So what are the best suggestions to making life more comfortable in the frigid winter waters, how do we deal with the elements and what are the danger signs and symptoms?

Firstly man is a homeotherm, that is he endeavours to keep his body core temperature constant irrespective of his surroundings. The body can be broken down into two main areas - the cooler outer 'shell' and warm inner 'core'. The core consists of the vital organs such as brain, lungs, heart and it is important that this is maintained at a constant 37°C. The shell consists of the skin, muscle, fat and limbs and is normally 3-5°C from the core. In cold climates the body achieves its constant temperature by a combination of heat production and heat conservation. In diving, hypothermia arises when the vital core is cooled as a result of exposure to the adverse conditions experienced underwater. Once you begin on the slippery slope of hypothermia, secondary problems such as narcosis and decompression sickness begin to increase drastically. We need to be able to combat the elements and there are a number of things we can do both in and out of the water.

1 EAT TO HEAT
The body needs high levels of energy to produce heat during a prolonged exposure. The main 'fuels' used by the body to generate this energy are carbohydrates. A diet based on carbohydrate foods (such as bread, potatoes, pasta, porridge, and rice) allows the body to stock your muscles with a plentiful supply. Man needs between 1,200 and 1,800 calories per day to maintain our base metabolism. On top of this you need to add in the order of 250 calories per hour of activity. When you add up the time spent loading up, kitting up, diving, de-kitting and packing away, plus an extra 10-20% to allow for the cold then the daily consumption can easily climb to levels of around 3,000 calories.

Prior to diving you can top up your levels by eating either commercially available high-energy bars or make your own. Two of the best homemade favourites are banana sandwiches and peanut butter and jam sandwiches. A nice big slice of Christmas cake is also great.

Warm drinks are also useful as both a 'morale booster' and a way of making sure that we are properly hydrated before a dive. Be careful however not to drink too much tea or coffee, both of which are diuretic and can cause dehydration. Something like warm Ribena or Vimto that has been well diluted with water is ideal. Good old hot Bovril or Oxo similarly diluted are also ideal.

2 LAYERS OF WARMTH
Assuming that the body core is nice and warm, then we need to build up an effective layer of clothing and protection to keep it that way. Starting with the base layer we need to use some form of thermal long-johns and T-shirt. We're not talking about the tatty old white ones (like Harold's dad used to wear in Steptoe & Son) today's thermal clothing has become quite trendy.
Even on the coldest days we will tend to sweat once we are sealed inside our drysuit and climb into our equipment. The idea of modern base layer clothing is that the sweat and moisture are actively transported or 'wicked' away from the skin so that as the sweat cools you don't feel the chill. Cotton T-shirts collect and hold the moisture and you end up with a cold clammy T-shirt covering the area where most of your vital organs are located!

Don't forget your feet either. A couple of pairs of polyester rich socks, topped with a nice thick pair of hiking style socks and a pair of thinsulate booties will give your feet a fighting chance of staying if not warm then bearable.

Next comes the mid-layer. There are dozens of mid-layer garments on the market. A pullover manufactured from a material such as Polartec or other polyester based fleeces have superb insulating properties, weigh nothing and continue the wicking process. Try to avoid really thick fleeces....you've still got to get your undersuit on yet. This may sound like common sense, but don't allow yourself to chill while you're setting up your kit. Get into your undersuit and suit as soon as possible. Not only are you then protected from the elements, but also you begin the process of pre-warming all your layers. Wear a warm hat to guard against heat loss from your head and if your hands are susceptible to the cold then wear some thin gloves.

3 IN THE WATER
Most readers know that gas divers tend to use an Argon suit inflation system to combat the heat loss due to helium and there is no reason why argon shouldn't be used during cold water diving. To get the real benefit of using argon you must flush your suit through before entering the water. With your zip and auto dump closed, pull your neck seal away a fraction and squat down. When all air has escaped replace the seal. Next inflate the suit with argon and repeat the flushing. This allows the argon to become trapped in your thermal layering and you will feel the benefit.
There is some debate as to whether an argon suit inflation system keeps you warm, or merely acts as a placebo i.e. making you believe that you're warmer! I don't know the answer - I've dived in so called extreme temperature undersuits and still felt cold, so obviously the placebo was wasted on me.

4 KEEP HANG TIMES REASONABLE
You don't have to be a genius to work out that the longer you're in the water, the colder you're going to get - no matter what steps you take to protect yourself. Plan your dive back to front agreeing run times first and then seeing what sort of bottom time is feasible (extra minutes on the bottom can mean tens of minutes on deco). Perhaps early January isn't the best time to be doing a 130 minute run time in the sound of Mull (is it Uncle Ken?!)

5 KEEP ACTIVE
As you decompress at the end of the dive try and keep mobile rather than hanging motionless in the water. Swim around the station if you're using one, if you're using a bag then turn around and fin gently (with the emphasis on gently) against the current. If you're using a jon-line off the main shot, then once again finning gently against the current will keep you active. The other benefit of gentle exercise when decompressing is to assist in off gassing your inert gas.

6 APRES DIVE
The simple fact of leaving the frigid water behind gives most people a feel-good factor. However, just because you're out of the water, don't think that the cooling effect isn't continuing. You have probably been in water that was a toasty 10 degrees while the surface is struggling to get above freezing. Be aware of the Wind Chill Factor - even the mildest winter wind places huge drain on the body's heat reserves and demands an extra output of energy.

If you have to stay in your suit, get your hands and head covered as soon as possible. The head has a strong blood flow and it has been calculated that as much as 75% of your inner warmth will be pouring out to the surrounding air. Get a warm drink inside you and take on some high-energy foods.

It can be quite obvious amongst a group of divers that one of the team is suffering the initial stages of hypothermia. They are the diver who is struggling to try and get their fins into a mask box! Seriously, keep an eye on those who are having problems with the simple tasks of packing away their kit or looking after themselves - they are warning signs. To undertake more adventurous dives during the winter is a serious undertaking. The hostility of operating in such an extreme environment both above and below the waves cannot be over estimated. This aspect of the sport pushes a diver, his team and their equipment to the limit.

However, taking these factors into consideration, to return from a challenging dive in the middle of winter gives us an enormous psychological boost that is hard to gain elsewhere. You get to know yourself a little more closely and when you close your eyes at night and recount the day's activity you drift off into a sleep that is like no other. Complete satisfaction.

HYPOTHERMIA
Listed below are the main symptoms and actions you should take if you suspect a diver is becoming hypothermic.

INITIAL SIGNS:
Feeling cold and tired. Not warming up and becoming mentally alert as the rest of the team does. Shivering. Numbness in extremities (hands & feet).

SECONDARY SIGNS:
Unreasonable and unexpected behavior. Physical and mental lethargy, constant yawning. Inability to respond to simple questions and directions. Lack of muscular co-ordination, erratic movements, falling. Difficulties with focussing, vision disturbance. The above are serious signs and immediate action needs to be taken to avoid a casualty slipping into unconsciousness.

TREATMENT
A simple hot drink, something to eat and getting the diver either properly covered (windproof jackets, blanket) or out of the elements (into a car, a boat's wheelhouse) will probably be all that is required to have the casualty begin to feel better.
Once in a warm environment replace any wet clothing. Monitor and reassure the casualty.
A hypothermic casualty aboard a RIB can be a serious incident. Get dive bags on the floor and sit the casualty on them. Get divers to huddle up to the casualty and try to cover all the divers with waterproofs.
Monitor the casualty. If respiration falters or ceases give artificial respiration. Monitor the pulse. If necessary commence cardiac massage. Get medical attention to the casualty ASAP.

By Rosemary Lunn.

WHERE TO DIVE THIS WINTER