first to cross the continent by land. but sea ice trapped then slowly sank "endurance." the crew survived on a diet of seals and penguins, and a spirit of camaraderie for 18 months. shackleton would rescue all 27 men, making him a legend. these modern explorers used drones to scan the sea floor. for weeks, they battled blizzards and shifting sea ice, though marine archaeologist mensun bound says thinner ice than usual helped. >> the ice is a lot more sparse, which is great for us, but probably not good news for the environment. >> reporter: in keeping with an international treaty, all they took from the ship were these images and data. >> it's about pushing the envelope with technology. daring to dream. >> reporter: and surviving by working together against all odds. roxana saberi, cbs news, london. >> diaz: against huge odds. next on the "cbs weekend news,"