Ocean Life Trivia: The Strangest Things in the Deep

We have mapped the surface of Mars in more detail than the floor of our own ocean. Most of the planet is water, most of that water is deep, and most of what lives down there we have barely met.

The record holders

• The blue whale is the largest animal that has ever lived — bigger than any dinosaur we know of.
• Octopuses have three hearts and blue blood; the copper-based haemocyanin that carries their oxygen is what gives it the colour.
• Sharks predate trees. They have been around roughly 400 million years.
• A starfish can regrow a lost arm; in some species, the arm can regrow the starfish.

Light in the dark

Below a few hundred metres, sunlight simply stops. What fills the gap is bioluminescence — animals producing their own light through chemistry. It is used to lure prey, to confuse predators, to find a mate, and it is not rare. In the deep ocean it is close to standard equipment.

The anglerfish, with its glowing lure hanging in front of its jaws, is the famous one. It is far from alone.

Pressure and cold

The deepest point of the ocean lies in the Mariana Trench, nearly eleven kilometres down. The pressure there is crushing, the temperature is barely above freezing, and there is still life. Whole ecosystems cluster around hydrothermal vents, powered not by sunlight but by chemicals venting from the sea floor — a discovery that changed what biologists thought life required.

Roughly seventy percent of the planet is covered by water, and we have properly explored a very small fraction of it. The strangest facts are probably still down there.