Antarctic scientists seeking the wreck of Sir Ernest Shackleton's lost ship, the Endurance, have arrived at the search site.
The team broke through thick pack ice on Sunday to reach the ship's last known position in the Weddell Sea.
Robotic submarines will now spend the next few days searching the seabed for the maritime symbol.
Shackleton and his crew had to abandon Endurance in 1915 when it was crushed by sea ice and sank in 3,000 m of water.
Their flight over the frozen floes on foot and in lifeboats is an extraordinary story that resonates over the years – making perhaps the most popular of all the undiscovered wrecks on wooden pole night.
The British-led Weddell Sea Expedition has given itself five days to find the sunken remains.
The team of the South African icebreaker SA Agulhas II plans to disable an autonomous underwater vehicle (AUV) in order to map the seabed for anomalies.
A wide box was selected, and the robot, equipped with a side-scan sonar, will run through this search zone like a lawnmower. The first dive lasts 45 hours.
It will not attempt to retrieve artifacts when Endurance is found. Only a 3D model of the wreckage is to be created.
The search becomes difficult because of the sea ice on the surface. The Agulhas have to periodically move their hulls to get open holes in the floes, through which AUVs are launched and salvaged.
The scientists are very confident that they are in the right place to find endurance.
Frank Worsely, skipper of Shackleton, was a very skilled navigator and used a sextant and a chronometer to calculate the exact coordinates of the endurance lowering – 68 ° 39 "30.0" south and 52 ° 26 "30.0" west.
The ship is almost certainly only a few nautical miles away from this point – and there is every chance that it is in a reasonable condition.
The organisms, which normally consume sunken wooden vessels, do not thrive in the cold waters of the Antarctic. Although the Endurance was broken when sinking, their wood is most likely well preserved on the seabed.
Going to the search page is a remarkable effort. The Agulhas had to fight through the thickened ice for several years.
However, unlike Shackleton, the Weddell Sea Expedition team has been supported by satellite ice maps, which greatly facilitate the search for a way through the floes.
The importance of the moment was not lost at the ocean archaeologist Mensun Bound of the expedition: "We are the first people here since Shackleton and his men!" he was quoted as said.