The success of the voyage depended on the pin-point accuracy of Worsley's navigation, using observations that would have to be made in the most unfavourable of conditions.[83] The prevailing wind was helpfully north-west, but the heavy sea conditions quickly soaked everything in icy water. Soon ice settled thickly on the boat, making her ride sluggishly. On 5 May, a north-westerly gale almost caused the boat's destruction as it faced what Shackleton described as the largest waves he had seen in 26 years at sea.[84] On 8 May, South Georgia was sighted, after a 14-day battle with the elements that had driven the boat party to their physical limits.