Diving under Sheet Ice
Diving under sheet ice is a specialized and and potentially risky form of diving. However , if it is carried out correctly it offers some unusual challenges to the sport diver.
Sheet ice can occur either on fresh water or, in constantly cold climes, on the sea. Once the water has frozen over, the wind cannot disturb the mass of water and any sediment tends to settle and visibility may become significantly better than normal for the area. Even in very cold water, life exists and with good visibility this can be enjoyed by the sport diver. The additional technical challenge of diving under ice can be a stimulus in itself. Whatever the challenge, the dive must be carried out safely and diving under ice demands special techniques.
By going under the ice divers cut off one very important escape route - the ascent to the surface and fresh air. Thus, problems that can be easily resolved normally must now be carefully considered. A freeflowing regulator which may be dealt with by a surface ascent under normal diving conditions now becomes catastrophic whilst under the ice. In the freezing conditions of the icy waters a freezing regulator and freeflow is much more likely, especially with warm-water piston operated regulators. With proper safeguards this problem can be overcome though.
Never dive under ice without a safety line, this should be tethered securely to the diver and to his tender on the surface. With this back-up in place a diver has a good chance of being saved in disaster.
Before the dive it is necessary to cut a hole in the ice. Adequate tools are needed for this task. Power tools are not uncommon. An ice axe is ideal, but other tools can be used. The hole should be big enough for at least two divers at a time. Some ice divers erect a temporary shelter around the ice hole for protection and shelter from the elements.
If you are cutting a hole in the middle of an ice field ensure that the ice can take a fully loaded divers weight, having to rescue the surface party is not a good way to get started in ice diving!
It may be a good idea to mark the hole underwater with something bright, an underwater strobe beacon is a good example. Having something like this will assist the divers underwater in locating the exit.
Because of the high risk if a diver becomes lost under ice, the emphasis should be on making sure that he does not, Divers should dive in pairs; each attached by a separate lifeline to a suitably experienced tender on the surface.
One lifeline with a buddy line to the second diver is not wise. A broken lifeline will then lose two divers. A stand-by diver should be ready to enter the water at a moments notice, no questions or hesitation! Every second a diver is in peril could cost his life, and a questing rescue diver can make all the difference.
Care should be taken that divers lifelines are securely attached to them. A bowline knot around the chest, under the equipment with the lifeline exiting behind and above. Only two divers should dive from one hole at any time, other ice holes should be made well away from each other, so as not to tangle the lifelines of other divers.
As many divers are well aware, the safety and well being of you're buddy is important. Ice diving makes this bond of brotherhood even more important. The dive should be abandoned if there is any malfunction of equipment. If a diver becomes detached from his line, his buddy must bring him back. If he becomes lost in spite of this safeguard, the buddy should return and the stand-by diver should enter the water. The best technique for finding a diver lost under ice is for the stand-by diver to go to the extremity of his line and carry out a circular sweep. By doing this he should, with luck, snag the lost diver, who can then return along the line to safety. If the first attempt fails, the sweep should be repeated on the bottom.
In addition to these diving procedures, the diver should pay special attention to his equipment. Environmentally protected first stages of diving regulators, octopus rigs and pony cylinders with a separate regulator have all a part to play.
Cold Water Diving | Ice Diving