Beneath British ice

IN THESE DAYS OF GLOBAL WARMING and stormy autumns that begin in July, we don't get that many decent freezes, in our southern counties at least. I understand that conditions are suitably tougher further north.
Ice-diving travel has broadened my appreciation of this chilly niche, but it doesn't offer the simple convenience of a Saturday-morning dive-club outing to the duck pond a few miles down the road.
But in the winter of 2008, things looked promising. By early December, the bookies were cutting the odds on a white Christmas. Snow fell across the country in mid-December, though it had cleared by Christmas Eve.
Nevertheless, it was bitterly cold, clear and dry by New Year, and stayed that way for the next few days.

RECONNAISSANCE
Snuggled up under the duvet on a Sunday morning, I kick my girlfriend out of bed for her morning run with instructions to extend her route as far as the pond to see if it's icing up yet.
An hour later, she has survived the treacherously slippery pavement and reports back that the pond was mostly iced over, with only small patches of clear water where the stream entered and exited.
I spend the next 15 minutes checking assorted weather forecasts for the coming week on the Internet. These are the same weather sites I normally visit to check the wind for a coming dive trip to the sea, except that now all I am interested in is how cold it will get, and whether it will stay below zero until next weekend.
A week of overnight temperatures well below freezing, and climbing just above zero on one or two days, looks very promising. I check with the club diving officer, then send a dive-trip invitation to the whole email list. Sometimes it's hard to remember how dive trips were organised before we had email.
Over the next few days, divers email back to sign up for a Saturday-morning ice dive.
Midweek, we're out for a pint at one of the floating bars in the docks. Over the course of the evening a skim of ice forms on the water outside. In a body of water as large as the docks it will no doubt break up over the next day, but the sight inspires a few more to sign up to ice-dive in the pond.
By Friday, it's time for a go or no-go decision. My girlfriend is at work, and as my preferred exercise is swimming rather than running, I drive to the pond for a recce. The ice is thick. We're on.
Compared to most trips, we don't need much kit. The water is shallow, so we require only a few single 10-litre cylinders between us. With a maximum of two divers in the water at a time, with one standby diver, we need only four sets of kit between us, including weightbelts.
With nothing to see at the bottom of the pond, the idea is to stay on the underside of the ice, so weightbelts are deliberately light, everyone dives buoyant, and BCs are of no value.
All regulators are diaphragm first stages; both more resistant to freezing and, if they do, more likely to freeze open rather than shut. Second-stage icing is less of an issue, as the daytime air temperature is above freezing.
This sort of kit optimisation won't work for every ice dive, but it makes sense in the limited confines of the pond. Additional equipment includes three ropes, two just under 15m long and one just over 30m long.
The short ropes are for the divers, the long one for the standby diver.
We also take some camping mats to sit and stand on, a couple of reels, because you never know when they could be useful, a small crowbar, a lumphammer and a saw. For really thick ice you would need a proper ice-saw, but for the thin ice we have on the pond an ordinary wood-saw will do.

CUT A HOLE
It would be nice to have ice thick enough to allows us to cut a hole out in the middle of the pond, but a quick inspection shows that this wouldn't work. The ice is simply not strong enough to take the weight of everyone close to the hole.
Instead, we pick a location on the footpath at the side of the pond, where everyone and everything can stand on firm ground.
On open ice, the hole would be triangular, so that a diver can get in and out at a corner of the triangle. By the side of the pond, divers can climb out at the wall, so we cut a semi-circular hole, for minimum stress on the ice.

SORT THOSE ROPES
We lay the ropes out along the footpath to make sure they are tangle-free, then tie one end of each rope to a convenient iron post. The other ends will be tied to the divers and standby diver, but not yet. First we have a dry practice at rope signals.
Ice-diving is conducted as a roped dive, so the diver just gets on with the diving while the rope tender keeps track of the time and exchanges rope signals with the diver to confirm that all is OK.
If anything goes wrong, in most cases the tender can simply haul the diver out.
The actual meaning of rope signals changes between diving projects, and whether it is the tender or the diver making the signal. For our dive, we work on a simplified set that anyone can learn and remember easily.
One pull is "OK", two means "End of rope" or "Give me more rope". Three pulls means "Slow down" or "Take up slack", four "Come back" or "I am returning".
Five or more continuous pulls signals an emergency, "Return now or I will haul you out" or "Haul me out".

FIRST DIVERS IN
The first divers are kitted up and tied to their ropes. We have selected some of the more experienced of those who have not ice-dived before.
Those with ice-diving experience are needed to control the surface procedures and act as standby diver while everyone else gets up to speed.
The ropes are threaded over one shoulder and under the other beneath the harness, and tied with a bowline. The usual freshwater safety briefing is repeated for everyone's benefit, though it is unlikely today that Weil's disease (leptospirosis) will be a hazard, as any rat's urine at the edges of the pond will be frozen solid.
The added briefing for ice-diving includes the instruction that, should anyone become detached from the rope, they should stay where they are for the standby diver to come and find them.
Diving buoyant, we know that they will be on the underside of the ice and not deeper in the 3m-deep pond.
Every few minutes, the tenders exchange OK signals with the divers. The divers have been warned that any failure to respond and they will be hauled out, so they pay close attention to their lines, and signals are reliably exchanged.

TURN & TURN ABOUT
After 20 minutes, the tenders signal four pulls to each diver to end the dive, and we all swap round.
The standby diver and one other now dive. A new standby diver sits roped up ready to go, with a camping mat to keep him warm. Tenders are also swapped, so that everyone builds experience at all the roles.
Nearly every diver has at least a small camera, so photography becomes the focus of those both below and above the ice. Those not diving or tending venture out onto the ice to try to photograph those below.
One of our basic safety rules is that no one goes on the ice unless they are fully suited up. Divers photograph each other, then turn their attention to taking pictures through the clear ice of those walking above.
We gather an audience as Saturday strollers and dog-walkers observe what's going on. Everyone is curious about what we're doing, why we're doing it and what we can see down there.
Of course, apart from the underside of the ice, there isn't really much to see at all. It's the simple, entrancing experience of floating beneath the ice and looking up at the world from below.
We change about again. Our single wetsuit diver has been in and, despite his claims of being comfortably warm, he is ordered back to his car to change before the cold sets in.
Those without a diving role are beginning to get restless. Some walk out further over the ice, with instructions to lie flat and spread the pressure if they feel the ice move. Despite cracks and groans, no one falls through.
Now it's time for an impromptu litter-clearance to get under way. Beer cans and other assorted rubbish thrown onto the ice over the past week or so are first curled to the side of the pond, and then into the litter-bin, which we also collect from where it has been dumped on the ice.
It carries over into the diving, as divers bring back rubbish and fishing-line from beneath the ice.
The white pond looks nicely clean again by the time the last divers have completed their under-ice experience, and we head off for a late pub lunch.

STAYING WARM
Even in a wetsuit, a short ice dive is endurable - as long as you're warm before and after the dive. Bring:

• A camping mat to stand on
• Fleece or ski gloves, hat and scarf
• An old coat two sizes too big to be worn over an undersuit or even over a drysuit or wetsuit
• An old sleeping bag
• Flask of hot water or camping stove
• Hotwater bottle (which can also be stuffed inside a drysuit or wetsuit for diving)
• Space blankets or plastic sheets to wrap up in and cut wind chill

REGULATOR FREEZING
Regulators can freeze in two ways. The first occurs when the air temperature is below freezing. Moisture in the first or second stage freezes before the dive, locking the regulator open or closed.

The second occurs as gas from the cylinder passes through the first or second stage, expanding and cooling. If the gas temperature is close to zero or below, the metal of the regulator can be cooled to the point at which ice forms. This is more likely to lock a regulator open, but closed freezing is not unknown.

To minimise freezing risk:

• Spend a few minutes almost on the surface in the ice-hole, allowing both stages of the regulator to match water temperature.
• Avoid filling a drysuit or BC while breathing in. Do not use octopus second stages. If an ice-dive means venturing far enough from the hole to warrant an alternative air source, it should be an independent regulator.
• Use a regulator with lots of metal in both stages, to improve heat transfer from the surrounding water.
• If a regulator freezes, immediately give repeated pulls on the line so that the tender can pull you out. If it freezes open, go on breathing as it free-flows.