Consider the possibility of icebergs, as the Telegraph reports:
More than 100 holidaymakers, including 24 Britons, were dramatically rescued from freezing waters in the Antarctic Ocean after abandoning ship when their cruise liner hit a submerged iceberg and began to sink.
The ice punched a hole in the 2,400-tonne liner, the MV Explorer, which began taking on water, forcing passengers and crew to flee on life rafts.
An international rescue operation involving coastguards on three continents was launched as the stricken ship was left listing at an angle of 45 degrees in the Bransfield Strait off the remote King George Island. It was about 75 miles north of the Antarctic Peninsula.
Argentine coastguards said they expected the vessel to sink later today.
After the ship issued a distress call other cruise liners headed for the scene and the drifting passengers were picked up by the Norwegian ship the NordNorge.