Endurance set sail from South Georgia on 5 December 1914, on the officially titled Imperial Trans-Antarctic Expedition. Two days later the ship hit pack ice and for the next six weeks made slow progress, edging ever closer to Antarctica. On 18 January 1915 they hit thick ice, and Shackleton decided to wait for a gap to emerge before continuing onwards. However, water froze around the ship overnight, trapping it in the pack ice.
After a few days, Shackleton realised he and his crew would be forced to wait until the Antarctic spring, many months away, for the ice to thaw.
This scene was described vividly by expedition photographer Frank Hurley in his diary: ‘It is beyond conception, even to us, that we are dwelling on a colossal ice raft, with but five feet of water separating us from 2,000 fathoms of ocean and drifting along under the caprices of wind and tides, to heaven knows where.’