Bizarre arctic brine plume forms a death-dealing tube of ice to the sea floor.

Plume descending as a tube of ice forms around it.

And having hit the ocean floor, it drifts along killing starfish.

A BBC team found a new phenomenon while filming a dense brine plume under the arctic ice.  It had been left behind when relatively salt-free surface ice formed.  As the plume sank carrying  bitter cold from the surface, the deeper water around it was transformed into a shroud of ice through which it passed.  When it hit the ocean floor, it left a traveling path of ice entombing hundreds of starfish.  The video at the link is time lapse photography since a foot a minute would be lickety-split for a starfish..