Turritopsis dohrnii, the “immortal jellyfish”, can revert to an earlier life stage when stressed, potentially repeating its life cycle.
Wacky Facts
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The deepest point reached by a diver on one breath is over 200 m.
Free-divers in the “no limits” category have descended beyond 200 m using weighted sleds.
The longest mountain range on Earth is underwater.
The mid-ocean ridge system winds about 65,000 km around the globe, mostly beneath the sea.
There are rivers and lakes at the bottom of the sea.
Brine pools are extremely salty water that is denser than seawater, so it settles on the seabed with visible “shorelines”.
Sound can travel thousands of kilometres through the ocean.
A layer called the SOFAR channel traps sound waves, letting whale calls and other low sounds travel huge distances.
Anglerfish carry their own light.
Deep-sea anglerfish have a glowing lure filled with light-producing bacteria to attract prey in the dark.
Most volcanic eruptions happen underwater.
The majority of Earth’s volcanic activity takes place on the ocean floor, especially along mid-ocean ridges.
1995Ocean waves can be taller than a 10-storey building.
Rogue waves more than twice the height of surrounding waves were once thought a myth; the Draupner wave in 1995 measured about 25.6 m.
Coral is an animal, not a plant.
Corals are colonies of tiny animals related to jellyfish. Many get their colour from algae living inside them.
More than 80% of the ocean has never been mapped in detail.
Only about a quarter of the seafloor had been mapped at high resolution by the early 2020s. The Seabed 2030 project aims to map all of it.
Sea water is salty partly because rain washes minerals off rocks.
Rivers carry dissolved salts to the ocean, and evaporation leaves them behind. On average seawater is about 3.5% salt.
The Great Barrier Reef is the largest structure built by living things.
Built by billions of tiny coral polyps, it stretches over 2,300 km off Australia and is visible from space.
The Mariana Trench is deeper than Everest is tall.
The Challenger Deep is about 10,900 m deep. Mount Everest, at 8,849 m, would disappear with over 2 km of water above its peak.
An ocean “conveyor belt” takes about 1,000 years to circle the globe.
The thermohaline circulation moves water between oceans driven by differences in temperature and salt.
The ocean produces around half of the oxygen we breathe.
Tiny marine plants called phytoplankton carry out a large share of Earth’s photosynthesis.
The Indian Ocean is the warmest ocean.
It is the third-largest ocean and has the warmest surface waters, which strongly influence the South Asian monsoon.
Whale songs can last hours.
Humpback whale songs are sequences repeated for hours, and all males in a region sing similar songs.
The Pacific Ocean shrinks a little every year.
Plate movements are slowly closing the Pacific while the Atlantic widens by a few centimetres a year.