Ice one, John!
You are toasting in front of an open fire, or snuggled under the duvet. The last thing on your mind is diving. But if it is cold enough to give a good freeze to ponds, rivers and lakes, as it was at this time last year, some maniac is sure to spoil it all by calling for an ice dive. It could be
John Liddiard
The first problem with ice-diving is finding the divers. You need more than a buddy; you need a rope-tender and standby divers. All the usual excuses come out. Even our club president is planning to wash his hair. I explain that this is a rare opportunity. I say they will regret it if they don't have a go.
Eventually the promise that we will be finished in time for lunch in a nice warm pub has the desired effect. Off goes our team to the local millpond.
Situated in a sheltered wooded valley, our dive site is protected from wind and acts as a suntrap on this bright morning. There is a good 6cm of clear, smooth ice over the water, thick enough to walk on.
Barely larger than a swimming pool and not as deep, the millpond is not the sort of location you would normally choose to dive. But when it is iced over it offers a unique experience.
We all suit up for safety before venturing onto the ice to cut a hole. Out come those traditional items of diving equipment, the lumphammer and chisel. Ice-divers in Canada use chainsaws, but a chainsaw would not be much use on a wreck. Anyway, cutting a diver-sized hole is a good warm-up exercise.
To avoid getting lost under the ice we use a sturdy rope, tended from the surface, rather than swimming out on a dive reel. You can't pull somebody out on a reel, and if the surface end is not tended, you might not notice if anything goes wrong.
Back in the good old days of BSAC Second Class Diver, a roped diver operation was a qualifying exercise. Now few divers have even read about it, so we have a few dry runs on the bank before going in.
One end of the rope is tied to a tree on the bank, the other threaded through my buddy's equipment and tied securely round my waist. The rope tender pays it out and takes in slack. For simplicity, we have just three signals: one tug for OK, two for "give me more line", and multiple frantic tugs for "pull me out fast".
Even wrapped up with an extra set of thermals under a drysuit and thick winter gloves, the water is bitterly cold. I bite hard on my regulator mouthpiece with the shock, and my face quickly goes numb.
I move out under the ice, making room for my buddy to slide through the hole and along the rope behind me. Trapped under the ice, our exhaust bubbles race in all directions. Eventually they settle to form wafer-thin pockets of air. Hitting the ice with a fist sends them racing again.
We explore the underside of the ice as our tender pays out more rope. The smooth surface is occasionally broken by branches. The clear ice acts as a diving mask to the world above, and through it we see clouds and trees.
Apart from my buddy, there is no life in sight, certainly none native to the pond. The rope tugs at me. Thinking it is an OK signal from the surface we return the tug, then give two tugs for more line, but none is forthcoming. We must have used it all.
Working back towards our entry hole, we pass areas where our exhaust bubbles have already started to melt canyons and pools into the ice. Standby divers are walking on the surface, looking through at us. We wave and try to write messages to each other.
Fingertips tingling, I follow my buddy back to our hole and escape to the surface. It seems an eternity, but my watch says just 20min and my dive computer hasn't even switched on; we haven't been deep enough!
We had deliberately cut our hole at the edge of the pond to make it easier to get in and out. Even so, we slip and slide, and need a helping hand.
Now it is the turn of the standby divers to dive, the next pair to act as standby, and my turn to warm up. The penalty for going in first is that we have to act as standby for the last pair to go in.
Rope will stop you getting lost; the other risk in ice-diving is regulator freeze-up. We keep our regulators warm and dry before entering the water, and although on this occasion we have no problems, we have contingency procedures.
We carry octopus regulators and independent air supplies, but have heard of a number of incidents where trying to use these in near-freezing water has caused further freeze problems. So our plans place priority on getting divers out rather than switching to alternative air supplies.
If a freeze-up occurs, the plan is to signal the tender and get pulled in as fast as possible. In the event of a free-flow the plan is the same, except that we continue to breathe from the free-flowing regulator. Our procedures, developed over a number of years, are a simple solution to the problems of exploring the frozen surface of our local millpond. Attempting more adventurous diving under ice will require other techniques. n
How to dive in winter and live to tell the tale
Regulator free-flows are the hazard to avoid when diving under ice, or in any water colder than 5*C.
The condition is caused by the sudden drop in pressure as air passes from cylinder to second stage. The effect is to cool the surrounding water even further as the air draws in heat, and the resulting ice can freeze up the regulator's moving parts.
To minimise the chance of this happening, make sure you and your buddy use regulators conforming to Euro standard EN250 (Cold Water Use).
Ensure that the cylinder and the air within it is remains as dry as possible. Keep it warm until the last moment.
Check the cylinder valve and other parts of the regulator and use warm air from the cylinder to blow away any water or ice trapped there. Between dives ensure that no water enters the air intake of the first stage when drying the dustcap.
Restrict yourself to no-stop dives at depths from which you can make a free ascent in an emergency. Do your check-out breaths in shallow water rather than in air.
Keep the second stage dry throughout your dives, and in your mouth at all times underwater. Heavy breathing or use of the purge button increases the cooling effect of the air flow, so try to avoid them.
Finally, be familiar with breathing from a free-flowing regulator, and make sure your buddy is too.
Appeared in DIVER - February 1998
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