Diving 1
Diving 2

One of the main problems with diving in Antarctica in the winter in particular is the difficulty of access to open water. There's plenty of sea around, it just has this big lid of ice on it. When it's up to about half a meter (16inches) thick a chainsaw with a particularly long ice-blade is the easiest way to get through it. All is well until you break through to the sea when you get showered with icy cold water for your efforts!

The approach is to cut out a big square, each side being about 1m (3 feet) or more, this floats when free at the same level it before it was cut free. The next thing is to cut this single piece into 4 equal sized blocks. If the ice isn't too thick and these pieces aren't too heavy, they can be lifted out of the water to keep them out of the way. If the ice is thick enough for these blocks to be very heavy, the technique is to push them under the water and to one side using a strong pole. As they will try to float, but are unable to, they will sit stuck up against the ice out of the way.

Having cut the hole, you then mark it with a painted pole and go off to get your mates to go for a dive. The first prospect of under-ice diving is pretty daunting, even for those who done this before it needs a particular focus.

I'm always reminded of a guy I met in Antarctica who like many of us, learned to dive there. However unlike most, his first ever dive was through a hole in the ice - he was pretty nervous as you can expect, but it was made worse by the dive-master getting his weight wrong, so as he slipped into the water, he immediately sank to the bottom in about 5m of water! Not something you want to experience given the choice, but a good story for the dive-club.

These guys deserve a special mention, they are professional divers and here they are about to do something partly at my request that I'm really glad I didn't have to do myself.

In the winter as a marine biologist I still had to carry on catching fish - in fact it was more important then than in the summer as it was far more difficult to get the fish then and far fewer people had ever caught them in the winter months or been around to record it for science.

The technique was to cut two holes about 100m apart as this was the length of a standard trammel net that we used. We drove a skidoo several times between the two holes to flatten any snow and to try to make the line obvious from beneath the water (and ice). The divers tied onto lines then dropped into the water and down to about 10-15m in 50-200m depth of blue-water, they had no points of reference other than the surface and each other, they swam the 100m to the next hole under the ice, following the skidoo trail before coming back up with the line at the second hole.

The line was then used to set and recover nets until the ice broke out. It always worried me that I might let go of the line and have to ask them to do this again - fortunately it never happened.

OK, so you've psyched yourself up to it, you've checked your equipment and your buddy's too, you checked and double checked the line you're tied to and it's time to go beneath the surface.

In reality of course, what is in your mind is far worse than the reality as when diving you hardly ever go back to the surface other than at the start and end of the dive, but when this entry/leave point is focused on a small square cut in the ice, it focuses the mind somewhat.

Notice the floating ice in the hole, dive holes would usually start to re-freeze between dives, but as long as they are visited regularly, they can be easily kept open with an axe and something to fish the broken up ice out of the hole with.

The key guy when diving under ice is the man at the surface on the other end of the line. There is a series of signals, pulls on the line to say "feed out", "take in" or "s**t! - drag us back now!" The line should be kept taught enough to pass signals, but not so taught as to make movement difficult for the divers and in an emergency the man at the surface could pull both divers manually back to the surface.

As a line man it's one of those very dull, and usually very cold (especially on the hands if you hadn't brought the right mitts to handle the wet rope) but vitally important jobs that you can't for a minute stop concentrating on. For most of us, the fact that on another occasion, we would be the ones under the ice concentrated the mind very well and helped to give the divers confidence in their mate at the surface.

There is also the fact that under-ice diving is FANTASTIC! so who cares about the extra effort if you get to do something so great.

When you get to dive under ice it is to normal diving what normal diving is to swimming on the surface.

I won't pretend I wasn't more nervous on these dives, but they were really unworldly and a fabulous experience. Your bubbles rise and stick against the underside of the ice making great silver mirrors as they do so. The dive hole that you worry you will lose before you go down becomes a great search-light shining down from the surface.

You see things in the water in these winter conditions that you never see otherwise, in this picture for instance, I'm swimming through a huge swarm of sea-creatures related to jellyfish called "Ctenophores" you can make out 3 of them oval-shaped objects behind me in the picture. There were literally thousands of them drifting slowly by, most are not visible in this picture. Ctenophores have bands of cilia that run their length and waft them along causing interference patterns as they do so, this looks like a monochrome world, but in reality I was surrounded by numberless rainbow phantoms.

Just got into the water and ready to go down - I'm already down to take this picture :o) Note the ice blocks that have been cut to make the dive hole stuck up against the ice, these are pushed under the ice with a pole as they're too heavy and difficult to get out of the dive hole.

This kind of diving is really like entering another world, more so than anything I've ever done. A great thing to do at the end of a dive when you have a little air left is to go up to the dive hole and take off your weight belt. You're then very buoyant and so can go back under the ice and walk around upside down on the underneath of the ice, if you lose your footing, you fall - up! Highly recommended to anyone who has ever thought about walking on the ceiling.

When the temperature drops in the sea, sometimes in the shallows ice starts to form below the surface as it is here. It starts as a nucleation point which can happen on submerged sea weed as here as delicate flakes of ice randomly forming ice crystals. In the shallows of 1-2m, ice may form on the sea bed from below as above.

Normally ice freezes from the surface of the water down as ice has a very unusual property amongst all substances in that as it turns from liquid to a solid, so it expands rather than contacts which is normal for cooling materials. This is why sea-ice floats rather than sinks as it would if it was almost anything else. The effect on the planet is profound, if water behaved "normally" then the oceans would be mainly solid ice other than the upper reaches and warmer climates.

Water has its maximum density at 4C and so all of the depths of the worlds oceans are at or around 4C as this temperature water descends due to it being denser than water around it of other temperatures.

The Antarctic Ocean is unique amongst the worlds oceans in that it has no Decapod Crustaceans - crabs and lobsters that are found in abundance in the rest of the world have never crossed the Antarctic Convergence, so their role is taken by other organisms of which this is one. Antarcturus signiensis has only been so far found in and around Signy Island and the South Orkneys where it is regularly encountered on dives down to 25m.

There are a whole host of organisms that take the place of Decapod crustaceans in Antarctica, many of which display signs of gigantism compared to their relatives elsewhere in the world. Underwater Antarctica is a place where entirely new species to science may be encountered.

What's the Viz? - It's how far you can see underwater. How many times did I hear that? In the winter in Antarctica, sea-ice forms and kills the ocean swell, this stops water movement stirring up any sediment in the water column which then settles out. After a few weeks, the visibility rises to a distance that is pretty much unknown in any other circumstances.

I recall seeing an horizon under water. The best "Viz" was at the end of winter when the sea hadn't been stirred up, but there wasn't a light-stopping ice layer, so you could see clearly through the water and there was plenty of light to see with. What's the Viz? 30m - 50m?, the optical effects of the water then stared to take over - but effectively it was as far as the eye could see.

Oh yes - sitting on an ice berg at about 15m in this shot and seeing how far I could see.

Diving on an ice-berg, what an ethereal experience! Well, yes it is in an "I've done that" sort of way, but actually it gets a bit dull beyond the first five minutes or so when you've taken the pictures of each other.

The berg is either no threat to at all - it's sitting there as a massive presence, like an underwater building, or there are a number of large "bergy bits" separate, but close and potentially moving. In that case, they are probably no threat, but you're not sure and you certainly don't want to get stuck between a couple of pieces of ice that weigh 1000 tons or more each.

I've also dived on bergs that are all sort of big crevasses and small caverns underneath which were dark and spooky and scared me in case I ended up up inside them and forgot how to get out again - this was probably more in my mind than reality, but I consider it a survival instinct worth listening to.

Diving on an ice-berg? do it once, get the pictures and don't bother again as it's actually a bit dull.

Emerging from a dive in Antarctica is like emerging from a dive anywhere else except more so. The underwater world of rocky faces and ledges is as vividly coloured as anywhere in the world, brightly coloured encrusting invertebrates with shells and fish. It's also not too cold thanks to what you're wearing, and under the ice it is of course all perfectly still, no waves, no swell.

Back on the surface the world becomes black white and blue again and all your diving gear weighs more than ever as you've extra weights to keep you down against the extra buoyancy of your suit, a result of it's extra insulating abilities.