We're finally in Antarctic waters, tearing a path through an ice field

We crossed into Antarctica on a clear, blue-skied morning at the weekend, just before 10am. The announcement came through over the Shokalskiy's public address system, followed by a muffled cheer from somewhere on the ship. The polar regions begin at a latitude of 60º South and the seas from there onwards are all part of the frozen continent.

The ship had been rolling around on the water for the best part of the past week but that had started to ease off as we made our way towards the colder waters further south. By 63º latitude, the sea had become calm, its motion dampened by floating chunks of ice, some as big as tennis courts, others several times bigger than the ship. An almost-infinite number of these snow-topped ice floes, a few metres thick above water but many more underneath, surrounded us and dotted the ocean all the way to the horizon.

The Shokalskiy's strengthened hull smashed through these rafts of ice with little trouble. As each piece disintegrated against the metal, inside the ship we heard bangs and felt the walls shudder. A few hours after we first saw it, a crowd had assembled on the bow of the ship to watch the Captain tear a path through the ice field. This was pack ice – ice that forms at sea and is blown around by wind and sea currents into huge patches in the polar seas.

While we were in the bows, an iceberg appeared out of the fog, off to our port side. The Captain slowed the ship and brought us to a cruise alongside the wall of ice, which was at least 50 metres high and hundreds of metres long. The surface of the iceberg was a pure, perfect white, pockmarked with caves and an occasional crevasse. Out of these cracks came an electric blue light, an ethereal window onto something inside that made the surrounding ice glow in the mist.

In the diaries of John George Hunter, the chief biologist on the original Australasian Antarctic Expedition, he described Douglas Mawson's team making bets about when they might see the first ice on their journey south. “Sea calm again but wind more round to the west,” he wrote at 59º south. “Again, very foggy. Everybody is on the lookout for ice but so far none has been sighted. Wild bet McLean a stick of chocolate we would see ice yesterday, but lost; and he lost the same bet today with Hannam.”

They eventually saw their first iceberg at a latitude of 63º south and the pack ice appeared at just after 65º south. On board the Shokalskiy, the winner of a similar bet to predict the location of the first iceberg had, by plotting the trajectory of the ship and correlating with weather data, managed to get an answer to almost the exact arc-minute of 63º 45' south, 147º 03' east.

The day after the iceberg, the fog had lifted. We woke to find that a few wispy cirrus clouds were the only blemishes on the bluest sky of our week at sea. The sun was high and bright but, despite appearances, the temperature of the air and water was only just above freezing.

The Shokalskiy had dropped anchor among the ice floes and we were told by the crew to put on sunscreen, lifejackets and as many of our layers as we could carry, and make our way to the gangplank on the starboard side of the vessel. There, a series of heavy-duty rubber dinghies, called Zodiacs, were waiting to take us on a ride through the islands of pack ice. In part, this was a chance to get up close and personal with some of the seals and penguins we could see sitting on the ice floes, but mostly it was training, a chance to start getting people used to the frigid temperatures and wind-chill of being outside on the Antarctic continent for long periods of time.

Within a few minutes, we had left the insistent hum of the ship's diesel engines behind and were surrounded by clear, cold, dark blue water. The scene looked almost tropical.

We picked our way between the floes, mooring alongside one and jumping onto it, like real explorers claiming a new land. We floated past three Adelie penguins on another floe that had no hesitation in coming right up to the edge of their ice, less than a metre from our Zodiac.

We watched a crabeater seal lazing in the sun and delicate, sparrow-sized snow petrels swooped in and out among the boats. Far away on the horizon, three enormous icebergs stood tall: irregular white boxes, big as city blocks.

After an hour among the ice, we re-boarded the Shokalskiy and swapped stories with people on the other Zodiacs. Some had visited our nearest building-sized iceberg, others had seen a whale near the ship. All of them had been charmed by the Adelie penguins. And then the ship's engines kicked back in and we moved on towards the Antarctic shoreline.

Though we are now only 100 miles or so from the continent, getting to our goal – Mawson's huts – will not be straightforward.

A few years ago, it was possible to take a ship straight in to Boat Harbour, the part of Commonwealth Bay where Mawson moored the Aurora to set up his base camp in 1911. Things got complex for potential visitors four years ago when an iceberg calved off into the Ross Sea, came around the coast of Antarctica and crashed into the Mertz glacier – named after one of Mawson's team who died on the epic trip over the ice in 1913 – on the edge of Commonwealth Bay.

This iceberg, B09B, became grounded at the coastline where Mawson built his huts and has remained stuck there ever since. This caused the whole bay to become iced up with fast ice, so-called because it sticks fast to the land.

Since there is no way to get a ship into Commonwealth Bay itself, we are planning to moor as close as possible, about 70km from the huts, and then send a small scout team to explore whether it is safe to land the rest of the ship's passengers. If this initial position doesn't work, the Shokalskiy's crew will keep their fingers crossed, hope that the weather plays ball and that the sea ice is not too thick for the ship to get through, and sail around the B09B iceberg to a backup location a few hundred kilometres down the coast. Again, a scout team will determine whether it is safe to land the rest of the Shokalskiy's passengers. Nothing is guaranteed.

Like the very first explorers of this region, the scientists and crew on board know that, however much they have planned, a lot of what happens next is out of their hands.

Highlight of the day: The penguins, seals and snow petrels

Lowlight of the day: The wind is picking up, and it gets right into your bones