We were so entranced by the wall of fluted ice at our fingertips that we never saw the dark shadow behind us. Slowly, it grew closer, emerging out of the dusky blue and stopping behind our backs. One of the divers happened to turn round, and there, just inches from his mask, was a set of furry nostrils.
It was a leopard seal, and it wasnt our first. The seals had been with us almost from the moment we hit the water. We had hoped to see them perhaps once on our trip. Who knew that they would show up on almost every dive
Leopard seals get their name from their spots - and their viciously predatory nature. But they eat penguins, not people - at least, not usually.
On that dive, the huge old bull circled curiously until his face was hardly a foot from mine. I could count the hairs on his cheeks. He poked his nose practically into my mask, darting forward in a feint that dive guide Adam Rheborg later explained was not so much a threat as a signal: Hey, Im bigger than you.
He certainly was.
Dive leader Goran Ehlme once spent an entire summer filming leopard seals. He said that he nearly had a stroke the first time one of them pulled this trick, but gradually realised that they simply wanted to play. In the end, he so bonded with one female that by the end of the season she was nuzzling his neck and bringing him half-dead penguins as gifts, like a cat bringing her kittens mice.
(I wasnt to know at the time that in late July a British Antarctic Survey scientific diver called Kirsty Brown would be pulled under water by a leopard seal and die while on a routine snorkel near Rothera Research Station. The attack was almost unprecedented.)
Im not sure what our group of divers expected to find under water in Antarctica. A bit of soft coral, perhaps. Some sponges, some starfish and a glimpse of penguins flying by. We knew that it wasnt going to be National Geographic Goes Under Ice, because all those films were made closer to the South Pole and involved technical diving. We were diving alongside, not under, the ice.
But no one expected the leopard seals, or the sheer beauty of the ice, not to mention the brilliant topside scenery.
We would slide into the water and spend our 30-40 minutes, and when we came up what greeted us was a wall of snowy rock, fissured glaciers flowing to the waterline and huge towers of ice that sometimes collapsed before our eyes.
The ice here is bigger, bolder and flatter than in the Arctic. Chunks of glacier the size of houses, of city blocks, of entire nations cleave off the continent and float like steroidal ice cubes.
We were there in late February, almost the end of the austral summer, and fresh snow dusted the mountains.
The farther south we went, the colder it became. The plus-seven temperatures of South America gave way to freezing the moment we crossed the 60th Parallel. And by the time we hit the Antarctic Circle at 66.5 south, we were in gale-force winds.
But most of the time it was sunny, if not particularly warm. And under water, the temperatures hovered at zero and sometimes sank to -1.5C (salt water can stay liquid almost to -2C).
We had left Ushuaia, at the southern tip of an island lying off the southern end of South America, on 28 February, and after two days crossing the Drake Passage, reached the Antarctic Peninsula. We spent a week there, travelling along the entire peninsula to the Antarctic Circle, with the chance to do two dives a day. But with so much also to see on land, it always came down to a choice - dive or hike
All 15 divers chose to visit Neko Harbour, one of the few penguin colonies with chicks this late in the season, and our only chance to set foot on the Antarctic mainland rather than offshore islands. The birds spread across a rising slope of snow furrowed with ditches worn by thousands of penguin feet.
It was almost too good to be real, with obliging penguins on the beach, some sunning themselves, some preening, many moulting, with patches of down still fluffing across their bodies.
Adolescent chicks, larger now than their parents, chased mums for food. Two Weddell seals lay on the beach and a leopard seal lurked just offshore. More penguins swam twitchily across the glass-smooth water. Behind all this, walls of square-cut ice rose in cracked columns that avalanched regularly, sometimes bringing down a 30m-wide face.
As the setting sun turned all this snow gold and then pink, we motored in the Zodiacs to the far end of the bay, where three humpback whales floated.
They blew clouds of fishy breath our way and rumbled like elephants. They were so close that we could count the bumps on their noses.
One dive was to the half-submerged wreck of an old whaling ship. The bow jutted 5m from the water and the rest of it went down to 18m, where the prop sat among anemones, nudibranchs, tiny starfish and a collection of whale-bones.
Another day, we dived Lemaire Channel at Deloncle Bay. Blades of kelp a metre wide waved in our faces. Behind this woven blanket lay a wall packed with life - large sunstars with dozens of arms, crinoids, sea cucumbers and basketstars, small as your palm in purple and neon orange.
Antarctic tourism has reached the point at which scuba trips are almost routine. Its fewer than 40 years since the first cruise ship began unloading the elderly rich at penguin rookeries. Even 10 years ago, a simple cruise here was the ultimate in exotic.
Now companies take skiers to the South Pole, climbers to interior peaks, kayakers along the peninsula and at least eight companies offer scuba.
Last season brought nearly 12,000 tourists to Antarctica. But while Lonely Planet guides now offer helpful hints on how to keep your eight-year-old amused between penguin visits, its also true that fewer than 500 of the yearly throng even make it to the Antarctic Circle.
Between diving and penguin colonies, we visited research stations. At Vernadsky, a Ukrainian station taken over from the UK for£1 (the coin is embedded in wood at the station bar), we learned that the average temperature here had risen 3C over the past 60 years.
The scientists at Vernadsky love tourists. The newly arrived winter-over crew explained that in two weeks five ships had visited, dropping£1300 for souvenirs. During peak season, its two ships a day. It helps pay the bills.
Nearby was the original British station, now a museum, left just as it was in the 1940s. The pantry was still stocked with old packs of biscuits, tins of art deco tuna and an ancient can of Ovaltine, along with the original typewriters, slide-rules, goggles and crampons.
At night aboard ship, the staff gave lectures. Goran told his leopard seal stories; Adam drew incredible birds on the chalkboard, then described them. Every spare minute was spent on deck or in the wheelhouse watching for birds, for icebergs and the occasional rainbow.
Our ice dive was at Pleneau Island, in a graveyard of ice chunks. Some were bigger than houses, but grounded, so there was no danger of them rolling onto us. We cruised the bergs, threading the Zodiac around sculpted blocks with deep blue furrows and feathered edges. Then we anchored next to one, dropped into the water and slid to the bottom at 25m.
The side was dimpled like a golfball and sunlight sparkled off the irregular edges. There were spires of white and small pockets of cobalt, all of it glistening as if it had been rubbed with oil.
And of course, there was the leopard seal. He spiralled out and up, then back in, twisting and circling around us. Every second or third pass, he would zoom right into my face, hold it for seconds, then dart off. This went on for a good 10 minutes - icebergs, shafts of sunlight and leopard seals (another had joined in).
Could it get any better Well, yes. Just as we surfaced, two penguins torpedoed by, leaping out of the water and bouncing, like so many skipping stones.
Cruising through grounded icebergs off Pleneau Island
diving at Pleneau
leopard seal encounter
a surfacing humpback whale, recognisable from its fins, which can reach a third of body length