A strange underwater phenomenon called "icicle of death" has been filmed by BBC crew in Antarctica.
Equipped with high end time-lapse cameras, the group recorded salt water being excluded from the sea ice and sinking down to the ocean floor. The temperature of this brine is below 0C, causing water to freeze in an icy casing called brinicle.
When 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. Read more here.