(11-11-10)Our friends from Argentina teach us to face dives in the frozen waters of mountain lakes and tell us their extreme diving experience in Patagonia, under the ice of Laguna Verde (Green Lake).

    Since the time when the German Heinrich dived in the Antarctic in 1901 many dives have been taken place under the ice, and technology has advanced a lot, and also materials. In fact, most of the world diving associations have this kind of diving as a SPECIALTY, with more followers each time.

    To dive under the ice it is needed to pass a specialty course that allows you to dive in cold waters and, in case it is needed, at altitude. It will make you dive in places that you won’t forget.

    Although it seems to be one of the less pleasant sort of diving for some, it is a unique experience that is worthy of living. The soft light filtering from outside, the ice layer on the surface protects the water and prevents the wind moving it. Sometimes, there is an awesome visibility, but not in most of the dives, depending on the environment we are diving in.

    It can be practiced in places with salt water or lakes or maybe frozen lagoons. A special training is needed, as well as having the specific knowledge, such as making a hole in the ice, tying a rope underwater, laying safety ropes for other divers, outside assistance with safety divers, etc.

CHARACTERISTICS OF A DIVE UNDER THE ICE

    Diving under the ice in lakes or lagoons in the Argentinean Patagonia has four main characteristics:

     1- It is high diving, most of the times. So, atmospheric pressure is lower than at sea level, and the risk of over-saturation is higher.

    On the other hand, the low temperature in water, associated to long times in the bottom, has a great influence in calculating the dives according to decompression tables in force (the less temperature, the higher gas absorption).

    Thus, tables will help correct depths (they will be lower always), and they are the more necessary the higher the height is.

    It would be convenient also to correct the speed of ascent, so that the absorption of nitrogen in tissues is lower. This is a factor that increases the risk of decompression accidents and has to be corrected in measuring devices. Those based on volume variations can make incorrect indications and depth gauges must be electronic. Capillary manometers are precise, but those of membrane or Bourdon, as they are referred to 1 Kg./cm2, are imprecise.

    It is mandatory to adapt from 12 to 14 hours in height before diving. It will prevent us from having a successive dive. Finally, we must not forget the potentiating effect that the wind has on the cold, inseparable friend in Patagonia!

    2- It is diving in fresh water. As it is not salt water, density is lower, so buoyancy is also lower.

    3- It is practiced in very cold water. Temperatures vary between 3º and 5º C. The low temperature of water increases the risk of hypothermia, so we need to know and review some concepts for when we dive:

    -Do not expose yourself to cold more than the strictly necessary, so the dives will be short, 20 to 30 minutes maximum.

    -Diving in good nutrition, hydration and rest conditions. Knowing and applying the emergency procedures when necessary.

    -Avoiding, if possible, making dives involving decompression.

    -Regarding the equipment: a dry suit is mandatory. Helmet and gloves of not less than 5 mm.

    -Given that the air we breathe and the one in the tanks must be completely dry to prevent humidity from freezing inside the regulator when consuming air, it is necessary that the controller has the first layer watertight. This way we avoid the air blocks by the formation of ice inside. Anyway, it is advisable, for safety, diving with two controllers with cooling kit installed.

    4- This is diving with real roof. As it is so, diving under ice has the same characteristics as diving in caves or caverns where the confusion is a constant, and where anxiety, distress, fear, mood or other pathological conditions of stress in general should be dominated by the diver, who, if is not able to do so, will have to abort the dive.

    However, diving under the ice, unlike in caves, permits the diver to be followed from the surface and extracted wherever he or she is if needed, when the thickness of the layer has the right conditions. It cannot be done when ice thickness exceeds 30 cm.

    Another significant difference is the following: while in diving under the ice the guide rope is controlled from the surface, when diving in caves the diver takes the reel him or herself. This is the reason why diving under the ice is considered as an intermediate step in preparing to cave diving.

THE IMPORTANCE OF SAFETY

    Conditions under the ice are so extreme that mates should always know the condition of the other. Apart from being alert in a closed environment, divers should be aware of their body temperature. If we want to repeat the dive, the body must be at warm temperature. To keep it so, energy-giving food and hot meals should be eaten.

    The basic diving equipment we are used to in situations of heat (wet suit) is not useful here. Apart from the dry suit, we must wear warm clothes under it, and thick dry gloves or gloves made of neoprene.

    We need a set of special controllers designed not to freeze if we are to dive in extremely cold water (Arctic and Antarctic). Before the dive, the regulator has to be in the water for a while to accustom it to the temperature. We only can breathe through it to avoid the risk of free flow, of uncontrolled release of air due to the freezing mechanism.

    It is recommended that the main source of air and the octopus are in the early separated stages to avoid the failure of both in case of freezing. 

    Some recommendations to take into account for this sort of diving can be the following:

    -Drilling the ice in places with a thickness not less than 25 cm. (Recommended)

    -Using power saws for drilling.

    -Drilling in a place that is completely covered by ice (thickness of 20 to 25 cm.) and assure a good stability. We must remember that it is important to distribute the weight of our equipment and our bodies HOMOGENOUSLY.

    -Drilling in a "triangular" way to prevent splitting and causing a risk situation.

    -Avoid square, rectangular or circular holes.

    -At least one person should be always placed on the surface with complete equipment for any emergency. If they are two, much better.

    -Take directions (coordinates) before starting.

    -If there are more people for supporting, they must be wearing isothermal suits so that, in case of breakage of the ice sheet, they can assist divers and not suffering from hypothermia. 

    -Divers should be tied to a guide rope, and to each other every two people. The distance should be about three to four meters. If there is a guide rope, they must be communicated to it through a "Join line."

    -Never exceed the 15 to 20 minutes of time on the seabed to avoid the risk of hypothermia.

    -The diver’s team must consist of 4 to 6 divers, as minimum, so the divers that are in the water are assisted by safety divers on the surface.

    -In the area, the divers will hoist the Flag ALFA of the International Code of Signals.