ice. With little to do since the Endurance became trapped, he occupied himself taking soundings of the ocean and collecting specimens. He later wrote a report titled Biological, Soundings and Magnetic Record, Weddell Sea, 1914–1916. By July, it was becoming obvious that the ice was likely to crush the Endurance, which creaked and trembled under the pressure, and Shackleton instructed Worsley to be prepared to quickly abandon ship if the need arose. Worsley was initially incredulous, asking Shackleton: "You seriously mean to tell me that the ship is doomed?" Shackleton responded, "The ship can't live in this, Skipper." Finally, on 24 October, the pressure of the ice caused the sternpost of the Endurance to twist and the ship began to quickly let in water. After desperate attempts to fix the leak and pump the ship dry, Shackleton gave the order to abandon ship three days later. Salvaging what essential supplies they could, the expedition set out on 30 October for Robertson Island, 320 km (200 miles) to the northeast. After just three days, it was clear that the condition of the ice was too rough for sledging. Having travelled only a 2.4 km (1.5 miles) from where the Endurance was sinking, they set up camp to wait for the ice to break up. Lumber and tents were salvaged from the crushed ship, which was still not fully submerged, and a reasonable camp, known as Ocean Camp, was established. The expedition stayed here for two months until 23 December, when they struck camp. The conditions underfoot were slushy during the day, as the temperature warmed up. Shackleton resolved to do most of the trekking at night, sledging the three lifeboats of the Endurance behind them. The sledging was hard work and after little more than a week, Shackleton and his men were forced to camp once more. Underneath, the ice continued to move northwards, and by April 1916, the floe they were on was nearly within sight of Elephant Island but beginning to break up. Shackleton ordered the expedition to the lifeboats, placing Worsley in charge of one of them, the Dudley Docker. It took a week to reach Elephant Island, the ice and currents inhibiting progress. The first few nights involved camping on nearby ice floes with the constant risk of them breaking up, but the last four nights were in the boats, with Worsley spending most of it at