50 mind-blowing facts about our oceans & marine life

A list of some truly unbelievable facts about our oceans and the weird and wonderful creatures that call them home.

In a slight change to the normal type of articles we produce, this post is simply a collection of some of our favourite facts about our oceans and marine life. It is by no means a definitive list or ranked in any particular order, it’s just some of our personal favourites. Enjoy!

1) The oceans are enormous

Our oceans cover around 71% of the Earth’s surface, but their depth means they actually contain 99.9% of the habitable space for life on Earth. They also contain 1.35 billion cubed kilometres of water!

The oceans cover over 2/3 of our planet’s surface

2) We haven’t explored most of them

Only 5% of the seafloor has been accurately mapped by scientists. In fact we know more about the surfaces of the moon and mars than we do about our own ocean floor. However new technological advances could hopefully be able to change this over the coming decades.

3) They are deep

The average depth of the ocean is 3,688 metres (12,100ft). The deepest point is 10,994 metres down at Challenger Deep in the Marianna Trench, where the pressure is a crushing eight tonnes per square inch! At this depth you could fit Mt Everest and the summit would still be over a mile below the surface.

4) They are dark

Because only the first few hundred metres of the ocean are illuminated by the sun and half the planet is constantly experiencing night time, up to 99% of the ocean is actually in complete darkness all the time. Yet this is something that we rarely consider when thinking about our oceans.

5) They actually move… very slowly

The global ocean conveyor belt, responsible for the constant movement of water around our oceans, moves much slower than wind or tidal driven currents. It is estimated to take a parcel of water up to 1000 years to complete a full cycle around it! It is also constantly moving over 100x more water than the Amazon River.

A diagram of the global ocean conveyor belt

6) They store a lot of stuff, even at the surface

The top 10 metres of our oceans has the same mass as our entire atmosphere, the top 2.5 metres holds an equivalent amount of heat and the top 2.5 centimetres holds as much water. The oceans also stores 38,000 gigatons of carbon (1 gigaton =1 billion tons), which is 16x more than the entire terrestrial biosphere.

7) The Pacific is the largest ocean

At its widest point (between Indonesia and Columbia) the Pacific Ocean is wider than the moon. In fact, at 12,300 miles across, it is 5x the diameter of the moon! It also contains over 25,000 islands.

8) The furthest point from land is closer to space

‘Point Nemo’ in the Pacific is the furthest point in the ocean from land, located over 1,000 miles from any landmass. Quite often the closest humans to this point are the astronauts on the International Space Station as they pass overhead.

9) The world’s longest mountain range is actually in the oceans

The Mid-Ocean Ridge, which stretches over 65,000km across the seafloor of all major oceans, is 4x longer than the Andes, Rockies and Himalayas combined!

The jagges white lines through the ocean show the location of the Mid-Ocean Ridge

10) The world’s largest waterfall is also in the ocean

The Denmark Straight Cataract, located in the Atlantic between Iceland and Greenland, is and sub-surface waterfall that consists of 5 million metres cubed of water continuously falling 3,505 metres (3x taller than Angel Falls). It is formed by a temperature difference either side of a large underwater ridge.

11) The oceans are full of treasure

Experts predict that there are more historical artefacts on the seafloor than in all of the world’s museums combined! UNESCO believes there are as many as 3 million shipwrecks in our oceans, each one brimming with a wealth of different historical treasures. There is also 20 million tonnes of gold in the oceans, most of which is dissolved in sea water at a concentration of a few parts per trillion.

12) World record scuba dive

The current world record for the deepest scuba dive is 332.5m, set by Ahmed Gabr in the Red Sea in 2014. It took him just 12 minutes to reach that depth, but it took over 15 hours for him to safely ascend to the surface!

13) Half of America is underwater

Because of its Exclusive Economic Zone (EEZ), which extends 200 miles along its long continental coastlines, Alaskan peninsula and other island territories, over half of the USA is actually in the ocean!

The darker blue regions of this map highlight that over half of the USA is underwater

14) Coral reefs are really important (and valuable)

Coral reefs only cover less than 1% of the seafloor, but support up to 1/4 of known marine species. Because of this they also provide food and income to hundreds of millions of people, in addition to storm protection and medicines. As a result they are currently valued at around $30 billion per year by NOAA (which many experts believe is actually an underestimate).

15) Most of the evolutionary history of life on Earth was spent underwater

Life originated in our oceans around 3.2 billion years ago, but only made its way onto land around 440 million years ago, meaning around 86% of evolutionary history was spent underwater. As a result there are also more major animals groups in our oceans (28) compared to on land (11). In fact up to 95% of life on Earth is found in the oceans!

16) Half the air we breathe comes from plankton

Trillions of photosynthetic microbes in the ocean, known as phytoplankton, produce as much oxygen as all the plants on land put together (some experts would argue it’s even more). This means that on average every other breath you take has come from the oceans, including oxygen produced by seagrass meadows and kelp forests.

Phytoplankton like these are responsible for over half the oxygen we breathe

17) The world’s biggest migration happens in the oceans… everyday

The largest animal migration by mass on the planet occurs in the ocean every single day and it’s not geographical, but vertical. Every night millions of deep-sea creatures travel thousands of metres upwards to feed on plankton that rise to the surface, before retreating back to the depths before morning. It is known as the Diel Vertical Migration.

18) The Sahara Desert is made up of dead plankton

The sand in the Sahara Desert is mostly made up of the skeletons of diatoms, a type of phytoplankton that live inside silica housing, who used to live in an ocean above Northern Africa millions of years ago.

19) Greenland sharks can live for over 400 years!

This means there are Greenland sharks currently swimming around the arctic that were born in the 1600’s. Researchers discovered this by looking at the levels of radioactivity in the growth rings of their eye lenses caused by cold war nuclear bomb tests.

Greenland sharks are capable of living for up to 400 years and maybe more

20) Dolphins have ‘X-ray vision’

Dolphins can technically see through other animals! The high pitched sound they produce for echolocation only rebounds of hard surface such as bone and cartilage, but passes through soft tissue. This allows them to see (or more accurately, hear) through other animals.

21) Corals can be used to replace human bone

The chemical composition and structure of some corals is so similar to our own bones, that they can actually be used in bone grafts! Some alterations have to be made to the coral before insertion, but it is actually beneficial for the patients who require less surgery.

22) Sharks don’t kill people… people kill sharks

On average less than 20 people are killed by sharks per year, but people kill over 11,500 sharks per hour! Keep that in mind the next time you hear about a ‘shark attack’.

It is estimated than 70 million sharks are killed every year for their fins to be sold illegally to Asia. So who are the real monsters here?

23) Sperm whales have the biggest nose in the animal kingdom

Sperm whales use their enormous snouts to create loud booming noises in the deep ocean, by reverberating sound waves in a large ‘drum’ in their noses. This is likely used for communication in the pitch black waters they hunt in.

24) Starfish can be born square

Some starfish suffer from an extremely rare birth defect and are actually square in shape! It can only happen to sea stars with five points and the exact nature of the mutation is still unknown.

An example of a square starfish, the reason behind this bizarre mutation is still unknown

25) World’s longest pregnancy happens in sharks

Frilled sharks have the longest gestation period of any vertebrate, capable of pregnancies as long as three and a half years (that’s 42 months!) and if that wasn’t bad enough the litter size can be as big as 15 offspring.

26) Size matters for rainbow octopuses

The blanket octopus (aka the rainbow octopus) have one the most extreme cases of sexual dimorphism (where different sexes are sized or shaped differently) in the animal kingdom. Whereas females grow to six feet in length, males only grow to be an inch long!

A female blanket octopus showing off her significant size compared to her male counterpart

27) Size doesn’t matter to harlequin shrimps

Harlequin shrimps feed on starfish up to 10x their size by flipping them over so they cannot escape. They will then feed on them throughout the next few days whilst they are still alive!

28) Great white sharks have LOTS of teeth

Great white sharks can lose well over 20,000 teeth in a lifetime! They can have around 300 teeth at any one time, most of which lie out of sight waiting to replace those that regularly fall out.

29) Pufferfish create elaborate nests

Male white-stripped pufferfish create one of the most intricate nests found anywhere on Earth. They create these beautiful mandala circles using only their anal fin and once they’ve attracted a female to mate with, they will guard the eggs in the centre of it.

An example of the mandala-style nests made by male white-striped pufferfish

30) Sea turtles ‘cry’ salt

Sea turtles cannot process all of the salt from the seawater they drink in their kidneys. Therefore they secrete excess salt through a gland below their eyes, often giving the impression they are crying when on land.

31) Baby sharks eat each other

The embryos of sand tiger sharks will eat their siblings inside their mother’s uterus. It is known as embryonic cannibalism and whilst a mother may start with 10 embryos (which can also belong to different dads) she will only ever give birth to a max of two.

32) Lobsters pee on their partners

The complex courtship behaviour between most lobster species actually involves urinating on each other. Lobsters can mix powerful pheromones into their urine which they use to communicate and also control one another’s behaviour.

33) Iguanas have trident-shape teeth

Marine iguanas have trident-shaped teeth that are specially designed for scraping algae off rocks. It gives them the appearance of little hands that wave at you from their gaping smiles.

The trident shape of marine iguana teeth helps them scrape algae off rocks

34) Little skates can regrow their cartilage

Little skates are the only known organism that are able to regrow and repair their own cartilage skeletons. This discovery has led to trials to see if the same technique can be used to do the same in humans.

35) Barnacles can act as whale GPS

The oxygen isotopes of barnacle shells can be used to track the migration routes of the whales they are attached to. In fact even fossilized barnacles can be used to do this for whales that lived millions of years ago!

36) Anglerfish have kinky sex

Some species of deep-sea anglerfish engage in a disturbing and bizarre behaviour known as sexual parasitism, where the dwarf males bite into and then fuse bodies with larger females, before spending the rest of their lives stuck together.

Two male anglerfish permanently fuse to a female via sexual parasitism, where they will spend the rest of their lives fertilising her eggs

37) Parrotfish poop out beaches

Most of the picturesque white sand on tropical beaches is actually parrotfish poop. These colourful reef fish scrape algae off corals, often eating just as much coral as algae, which they break down and excrete as sand. The average parrotfish will poop out over 100kg of sand a year.

38) Mantis shrimp pack a punch

The mantis shrimp has the most powerful punch in the animal kingdom. They can strike their claws at 50mph with the equivalent force of a .22 calibre bullet and can even create sparks underwater!

A mantis shrimp prepares to strike with its club-like apendages

39) Deep sea fish can be really dark

There are 16 species of ultra-black fish, whose skin absorbs over 99.5% of the light that hits them. This allows them to remain practically invisible in the deep ocean and sneak up on their prey, whilst avoiding predators.

40) Pygmy seahorses don’t move much

Some pygmy seahorses stay on the same sea fan their entire life and may only ever move around within an area the size of a dinner plate.

41) Sea sponges are older than the dinosaurs

Sea sponges were around more than 640 million years ago. Experts believe they are closely related to the very first multi-cellular organism. They can also live for over 11,000 years, making them the most long lived animals ever!

42) The deepest recorded fish is a ghost

The deepest living fish ever recorded is the ghost fish, filmed during a dive into the Mariana Trench at a depth of 8,143m!

This ghost fish is the deepest recorded living fish

43) Basking sharks actually have teeth

Despite being filter feeders that only consume plankton and other micro-organisms, basking sharks do actually have teeth. Their residual gnashers only grow to a tiny 2mm in length and despite having little use for them they still have around 1,500 of them.

44) Longest mammal migration occurs in whales

The longest known mammal migration was achieved by a gray whale travelling 22,511km over the course of 172 days!

A gray whale and her calf travel across the open ocean

45) Octopuses have three hearts and blue blood

Octopuses actually have 3 hearts, a systemic heart which pumps blood around the body and 2 branchial hearts that pump it through their gills. If that wasn’t weird enough their blood is also blue, because it contains copper instead of iron.

46) Seaweeds can be really useful

Special compounds extracted for the cell walls of brown algae, known as alginates, are used widely in everyday products including beer, ice cream, adhesives, ceramics, paper, explosives, waterproof fabrics and antacids, as well as being trialled in bone and brain tissue regeneration experiments.

47) Some crabs wear living boxing gloves

Boxer crabs use anemones as ‘boxing gloves’ to fight off predators. In this form of symbiosis the anemones get free travel and food in return for being used as a stinging weapon to protect its crustacean host.

A boxer crab shows off its symbiotic stinging boxing gloves

48) Dolphins have accents and dialects

Researchers have shown that distinct groups of dolphins from the same species show variation in the sounds they make to communicate. This is one of the strongest pieces of evidence that these cetaceans have actually developed a language which is passed down through generations.

49) Over 60% of octopus cognition happens in their arms

Unlike most other animals, octopus neural networks actually extend out of their centralized brain and into their arms. This means each arm has its own ‘separate’ brain and can act individually from the rest of the body, this is what allows them to have such incredible control over their arms and individual suckers. Because they can re-grow detached arms, this also means they have the ability to re-grow brain tissue.

50) Marine animal group names are the best!

To finish of the list here’s a list of some of the coolest marine animal group names…

  • Squid – an audience
  • Lobsters – a risk
  • Sharks – a shiver
  • Stingrays – a fever
  • Manta rays –  a squadron
  • Fish (generally) – a school
  • Barracuda – a battery
  • Herring – an army
  • Sea turtles – a bale or nest
  • Clams & oysters – a bed
  • Dolphins – a pod
  • Sea otters – a romp
  • Crabs & octopuses – a consortium
  • Sea urchins & whales – a herd
  • Jellyfish – a fluther, bloom or smack
  • Sea birds – a wreck
  • Starfish – a galaxy

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