A brinicle sounds like something from a sci-fi movie: a finger of ice slowly descending from above, freezing everything it touches and leaving a trail of frozen corpses. In fact it is an unusual underwater phenomenon, sometimes found in the Antarctic Ocean.
The name brinicle is a combination of brine and icicle, and they grow downwards from sheet ice. The freezing process forces out salt, creating intensely cold, salty water that does not freeze because of the salt concentration. This is heavier than normal sea water and so tends to sink.
