did he make any open-boat journey?
Yes, he risked such a journey to the 720-nautical-mile-distant South Georgia whaling stations.
Ernest Shackleton
Consequently, Shackleton decided to risk an open-boat journey to the 720-nautical-mile-distant South Georgia whaling stations, where he knew help was available. 
what is farthest south? It is the most  southerly latitude reached by explorers before the conquest of the South Pole in 1911. who led the explorers? Robert Falcon Scott and Ernest Shackleton what is the nationality of the latter? He is Irish can you name any of his expeditions? The "Discovery" expedition, the "Nimrod" expedition what was discovered in the latter? Barrier Inlet did his exploration brought him fame? Commander of the Royal Victorian Order where did he carry out his final expedition? The Antarctic what was his profession before becoming an explorer? Merchant Navy officer where was he posted? UNANSWERABLE
wiki:5384492
Ernest Shackleton [SEP] Open-boat journey
Elephant Island was an inhospitable place, far from any shipping routes; rescue by means of chance discovery was very unlikely. Consequently, Shackleton decided to risk an open-boat journey to the 720-nautical-mile-distant South Georgia whaling stations, where he knew help was available. The strongest of the tiny lifeboats, christened after the expedition's chief sponsor, was chosen for the trip. Ship's carpenter Harry McNish made various improvements, including raising the sides, strengthening the keel, building a makeshift deck of wood and canvas, and sealing the work with oil paint and seal blood. Shackleton chose five companions for the journey: Frank Worsley, "Endurance"s captain, who would be responsible for navigation; Tom Crean, who had "begged to go"; two strong sailors in John Vincent and Timothy McCarthy, and finally the carpenter McNish.