BBC captured this incredible footage of a underwater icicle forming. The salty water, which has a temperature lower than zero degrees, causes the water around it to freeze. The result is an icicle that makes it’s way to the bottom of the sea and leaves a frozen path of destruction. Poor starfish never saw it coming!

With timelapse cameras, specialists recorded salt water being excluded from the sea ice and sinking.
The temperature of this sinking brine, which was well below 0C, caused the water to freeze in an icy sheath around it.
Where the so-called “brinicle” met the sea bed, a web of ice formed that froze everything it touched, including sea urchins and starfish.
The unusual phenomenon was filmed for the first time by cameramen Hugh Miller and Doug Anderson for the BBC One series Frozen Planet. – BBC

Link: BBC Nature: ‘Brinicle’ ice finger of death filmed in Antarctic