Death by Brinicle

1

The brine sinks because it is more dense than the surrounding water. The formation of the brinicle was filmed in 2011 for the BBC series Frozen Planet.

2

Any bottom-dwelling sea creatures, such as starfish or sea urchins can be caught in this expanding web of ice and be trapped, and ultimately freeze.

https://youtu.be/Nf8b_IQv-rw