In the video below the fold from the new nature special Frozen Planet, time lasped photography captures a deadly growing brinacle. What is a brinacle you ask? When sea water freeze on the surface it forces salt out as a briny fluid. The brine is heavier than the underlying sea water, it percolates down through cracks in the growing floes and creates a sort of stalactite that reaches to the bottom and flows like a creek, freezing everything in its path. It’s fascinating and a little creepy.