The Hourglass dolphin, "Lagenorhynchus cruciger", is small and wide compared to other dolphins. It only lives in the very cold waters of the Antarctic. It was not known to science until a drawing was made of it in 1820. Only six Hourglass dolphins have been examined by scientists. Boats do not usually go where they live. The average water temperature they live in is 0.1-0.3 degrees Celsius.