Sous la mer

As sea water freezes to form surface ice, the remaining brine sinks, being much denser and colder than the surrounding water. As it descends, the surrounding water freezes upon contact, creating a ‘brinicle’, a frozen sheath of ice that grows downward towards the sea floor. When it touches the sea floor, it kills anything it touches, encasing them in a tomb of ice.

Attenborough narrated video - BBC

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