It's arguably the most famous shipwreck whose location has yet to be found.
The Endurance vessel, which was lost on Antarctic explorer Ernest Shackleton's ill-fated expedition in 1914-17, lies at the bottom of the Weddell Sea.
Many have thought about trying to identify its resting place; a few have even had a go. But sea-ice cover in the region makes navigation very tricky.
Dr John Shears and colleagues, however, are undaunted. Having been beaten on their last mission, they're returning.