Amazing columns rose from the stony floor of the fjord in great, wiggly spires, some continuing up to within 3m of the surface. They were as varied as they were numerous, standing clustered in small groups or alone, like isolated trees in a forest clearing.

I was diving last summer in the cold waters of Ikka Fjord on Greenlands southern coast - not your everyday diving destination - as a member of the Imperial College Diving Expedition to Greenland.

Our aim was to study ikaite, a rare mineral from which these columns were formed. Normally found on ocean floors, ikaite grows from springs issuing through joints in the underlying rock, and exists in only a few shallow sites - in Greenland, Japan, California and Alaska. In Ikka Fjords column structures we were, though, seeing something unique, for other shallow-water ikaite exists only in flatter reef form.

Four of our six-strong team - mainly geology post-graduates from Imperial College and other London institutions - were BSAC college branch members: an Advanced Instructor, Advanced Diver, Dive Leader and Sports Diver. Between us we had trained up the other two members of the expedition.

May 95 saw the shipping out of our boat, dive kit, compressor, generator, tents and food to a Danish naval base in southern Greenland. In early July we made our own, tortuous journey, with flights to Copenhagen and Narsarsuaq, an old American air base in southern Greenland; then (to save money) a 50km walk across mountains while our personal luggage continued by ship to a port near Ikka.

From our camp set in Ikkas mystical surroundings, we started our 4-week stay by charting the fjord, surveying the shore at high water to establish a baseline, then noting depths along traverses using GPS and an echo sounder. We plotted the major positions of ikaite and pegged out underwater survey lines.

Our superb columns lay mainly near the head of the fjord. They rose from a maximum depth of 28mt, but our average diving depth was 15m or less.

The more slender, delicate pillars, were spectacular - only a few centimetres in diameter but rising several metres from the bottom.

By contrast, massively broad growths, metres wide, rose up a full 18m towards the surface. They would terminate in clusters of knobbly spires, often growing into each other, like the flying buttresses of some great cathedral.

Having mapped, examined and photographed the columns, we moved further south down the fjord, where the ikaite occurred in flatter, reef-like form. Even here, though, it grew sometimes like fingers in lines, joined together like webbed hands or corrugated curtains.

Throughout, we took samples of ikaite for analysis back in London. This was a delicate procedure as the mineral, a hydrated form of calcium carbonate, is unstable, crumbling to powder if exposed to the air.

Apart from our studies of the ikaite, we were delighted to find extensive marine life where we had expected the fjord to be desolate. The floor was alive and kicking with anemones, crabs, starfish, sea cucumbers, sea urchins, sea slugs, boring bivalves, edible muscles, sea squirts and algae.

Other companions included Arctic char, plaice and sea scorpions, which followed us around inquisitively wherever we roamed. Jellyfish were pretty common, too. Occasionally it was hard to tell whether our lips suffered from the cold or their stings.

During summer, when we dived, the fjord is generally ice-free and receives a continuous supply of water. This gives a surface layer of fresh water up to 4m deep, overlying the sea water. This led to some interesting diving experiences. The average surface temperature was about 13Â C, but then you would hit the seawater and it would drop to about 2Â C or, sometimes, nearly zero (sea water freezes at about -1.8Â C).

Careful buoyancy control was called for because, at the sea to freshwater interface, we would find ourselves suddenly negatively buoyant on approaching the surface at the end of a dive.

Visibility was usually excellent in the first 5-6m and good at 8m, although towards the end of our stay it decreased due to plankton. Working on the fjord bottom, as we did a lot, visibility was often zero.

All of which made our attempts to photograph the ikaite structures quite tricky, for we were geologists first, photographers a decided second! We did the best we could with two Nikonos V cameras and a housed Sony Hi 8 video camera.

As ever, safety was paramount. We had an oxygen kit but, as the nearest recompression facilities were in Canada, we played safe on dive profiles - all no-stop dives using the BSAC 88 Tables. To avoid rapid ascents in the event of a free-flow or air depletion, we all carried a twin set or pony with independent regulators.

With our drysuits we used wet hoods and gloves; dry gloves were tried but were awkward to use and generally abandoned. August bodies back home shared our enthusiasm for the project, so that £7000 of the expeditions £20,000 cost was donated by the Royal Geographical Society, British Sub-Aqua Jubilee Trust, Scott Polar Research Institute, Imperial College Exploration Board, Rolex and others. We covered the rest individually.

Scientists from Copenhagen University have visited the fjord to study the unusual ecosystem and geochemistry of the water, and now members of both our expeditions are working together on the science of the region.

Following on from our joint studies, the Greenlandic Government plans to designate Ikka Fjord as a World Heritage Site, to which access will be carefully restricted. I am certainly privileged to have experienced its wonders.