Making up more than 70% of the Earth's surface, the world's oceans are vast and deep. There are about a million species living in the ocean today, which make up our most crucial ecosystem.
What's even cooler is that we are still discovering new species all the time!
About 80% of our oceans are still unexplored.
For now, however, we can explore and appreciate the thousands of ocean animals we know about.
Come dive in with us as we explore the beautiful sea creatures in the world's oceans.
Animals That Live In The Ocean
As we said before, the ocean covers more than 70% of the Earth's surface. Beyond that, oceans are incredibly deep, meaning fish and other marine animals fill the oceans from bottom to top, from the sea floor to the water's surface.
In addition to marine animals, the sea is filled with ocean plants, which provide homes, food, and protection for sea creatures.
Some of the smallest animals in the ocean are plankton. This unique species makes its home in the sunlight zone, living through a process known as photosynthesis, in which they convert light into energy. Plankton is a major source of food for many sea animals, including fish, anemones, and scallops.
Essentially, plankton is where life starts in the ocean.
Let's break down some categories of ocean animals and explore them individually.
Most Popular Fish Species:
Fish are cold-blooded vertebrate animals (with the exception of mackerel and tuna). To be cold-blooded means their blood and body temperature adjusts to the temperature of the surrounding water. This characteristic is different from humans, who always have a body temperature that hovers around 98.6 degrees.
Fish have gills, which they use to take in oxygen. Unlike some other ocean animals, fish cannot live outside of the water, as they are unable to breathe air.
Most ocean fish spend their entire lives in salt water. However, rainbow trout are born in fresh water before making their way to the ocean.
To swim from one place to the next, they must use their tails and fins. Many fish have swim bladders inside of them, which fill with air and allow them to float through the water. Fish have control of the amount of air in their swim bladders too. If they want to move further toward the surface, they can let more air into their swim bladder, and if they want to go deeper, they can let the air out.
Fish don't give live birth. Instead, they lay eggs, which baby fish hatch from.
FUN FACT - Scientists have uncovered over 28,000 species of fish, though with so much of the Earth unexplored, they believe there are many more to be discovered!
Note that some species have the word "fish" in the name, though they are not considered fish. These species include jellyfish, which are plankton, cuttlefish, which are mollusks, and starfish, which are "echinoderms."
Most Popular Shark Species:
While sharks are technically fish, we like to categorize them all on their own because of their unique characteristics!
For starters, unlike most fish, shark species do not have bones in their skeletons. Instead, their skeletons are composed of cartilage, which is the same material found in your nose and ears. However, while sharks do not have bones, they are very similar to bony fish in many ways.
They breathe through their gills and are cold-blooded animals. To tear off large chunks of food to consume, sharks have several rows of sharp, pointy teeth. Unlike humans, sharks don't chew their food, but instead, they swallow it whole. Sharks will often lose their teeth, though they almost always grow new ones in place!
While a shark's diet fluctuates depending on the region it lives in and the food available, some of the most popular shark prey include squid, fish, sea turtles, marine mammals, sea lions and seals! Sharks have a killer sense of smell, which is how they're able to find food so easily. While they spend most of their time hunting near the water's surface, they sometimes dive deep to look for food.
Contrary to popular belief, not all shark species are large. In fact, some small sharks only ever grow to around seven inches in length. Sharks that most people are familiar with often grow to around 5 to 7 feet, very similar to the size of your average adult human.
Sharks often get a bad rap as being "dangerous" to humans. However, many sharks don't present any danger. We're more of a threat to them than they are to us! Out of more than 350 types of sharks in the ocean, we only know of 25 that have ever attacked humans. Beyond that, most sharks only ever attack humans because they mistake them for seals or other ocean animals that are part of their diet.
FUN FACT - Baby sharks are called "pups" (adorable, right?). While most pups hatch from eggs, some grow inside of their mothers.
Most Popular Ray Species:
Rays are a type of fish that are closely related to sharks. Instead of bones, they are made of cartilage. Rays look like flat fish with long tails, gills on their undersides, and eyes on the tops of their heads.
While most rays live their lives in large groups, some prefer to live alone. There are a few ray species that have poisonous tails, which they use to stun or kill prey. Other rays filter small bits of food in the water, similar to the way baleen whales eat.
As with many ocean animals, rays can vary a lot in size.
FUN FACT - Some of the biggest rays in the ocean are called manta rays. These rays can grow to be more than 20 feet wide!
Most Popular Ocean Mammal Species:
Marine mammals make up a large portion of the ocean. These creatures include whales, walruses, porpoises, dolphins, seals, dugongs, manatees, and sea otters. There are few mammal species, including sea otters and seals, which also spend parts of their lives on land.
Marine mammals are an incredibly diverse part of marine life. We can break down these ocean mammals into four groups:
Some key ways to differentiate mammals from other ocean life are that they are warm-blooded, breathe air with lungs, and give birth to live instead of laying eggs. Because mammals have lungs instead of gills, they must breathe air. Dolphins and whales, for example, have, blowholes that they use to breathe air from above the water's surface.
Many marine mammals have some form of hair or fur, though it may fall out by the time they reach adulthood.
Whales are certainly the most impressive marine mammals. They often live in pods, which are basically families of whales that take care of one another. Like adult humans take care of their children, adult whales take care of their calves.
Most whales are found living close to the surface, as they must go up for air often. This may lead you to wonder, "how do whales sleep, then?" Find out in our recent article!
It's important to understand that there are two types of whales in the ocean:
Baleen whales, which include gray whales, blue whales, and humpback whales, are some of the largest animals in the world, trumping most toothed whales in terms of sheer size.
The blue whale is the largest animal on Earth, often growing up to 110 feet long and weighing around 300,000 pounds!
Baleen whales feed using baleen plates, which are comb-like plates made of keratin (the same material found in your nails).
They'll filter the water around them to take in small bits of food, including krill and small fish.
FUN FACT - Baleen whales have not one but TWO blowholes!
Toothed whales, which include orcas (killer whales), sperm whales, and belugas, have teeth, which they use to consume larger prey.
These whales use echolocation to determine how close or far away they are from objects. Echolocation is a unique trait that allows them to find food.
Some favorite toothed whale dishes include squid, fish, seals, and other animals.
Killer whales even go so far as to eat other kinds of whales! The sperm whale is the largest of the bunch and the only toothed whale able to consume a giant squid!
Most marine mammals live in colder parts of the ocean, using blubber, a thick layer of fat between their organs and skin, as insulation to maintain body warmth. A layer of gray whale blubber, for example, is around 10 inches thick!
Mollusks are invertebrates, meaning they have soft bodies and lack backbones. It is astounding just how diverse the mollusk family is. Some have hard shells, which they use to protect their soft bodies, though many do not.
We can break mollusks down into five main classes, including:
Some of the most popular mollusk species include scallops, squid, and cuttlefish.
Let's take a look at some of these mollusks individually.
While there are many types of squid in the ocean, arguably the most popular squid species is the giant squid.
A giant squid can reach up to 40 feet in length and weigh more than 2,000 pounds!
One of the few predators able to take on the giant squid is the sperm whale, though even sperm whales must put up a serious fight in order to eat one.
The giant squid has eight arms with two extremely long tentacles.
At the end of its tentacles are sharp barbs, which it uses to capture its prey, including fish and smaller squid. Because giant squids have such large eyes, they are able to see exceptionally well under the depths of the ocean where hardly any light is present.
While the cuttlefish sounds like one of those cute ocean animals, they are part of the family of cephalopods, which include squid and octopi.
These creatures are incredibly unique, as they have the ability to change their skin colors and patterns to blend in with their environment.
Cuttlefish catch their prey using several arms or tentacles and are incredibly fast swimmers. Many of them are poisonous, using a lethal toxic compound to kill their prey.
Scallops are bivalves, just like oysters and clams.
These small animals live between two identical shells and spend their lives on the ocean floor.
They can move by opening and closing their shells, squirting water out to propel them from place to place.
Many bivalves eat plankton, though some eat other small ocean life, such as algae.
There are 289 species of octopus known to man, some of which are dangerous to humans.
These mollusks have eight arms, large heads, blue blood, three hearts, and ink that they squirt to deter predators and confuse prey. Octopi might be some of the most intelligent species known to man, and some have even been observed using tools!
Most octopus species have an incredible sense of touch, as their suckers have unique receptors that allow them to taste the things they touch.
Unfortunately for octopi, both the males and females die very soon after mating.
While most reptiles spend their time in freshwater or living on dry land, many species spend their lives in the ocean. Some of the most well-known oceanic reptile species are sea turtles and sea snakes. Marine reptiles are broken down into four main groups:
Sea turtles can live for up to 50 years or more, often taking decades to reach maturity. They can swim effortlessly in the ocean, diving very deep to escape danger or find food. See the biggest turtle in the world!
There are two groups of sea snakes, including true sea snakes and sea kraits. Sea kraits can go on land, as they don't have traits that have fully adapted them to water. True sea snakes, on the other hand, are evolved to thrive completely in water.
There are 69 species of sea snakes, most of which are venomous and live in the Indian and western Pacific Oceans. Many sea snakes make homes in estuaries or coral reefs. The only species that lives in open waters is the yellow-bellied sea snake.
All reptiles are cold-blooded and must go to the surface every now and then for air.
People don't often think of birds when they think of ocean animals. However, while there aren't any bird species that live in the ocean, there are many types of birds that spend the majority of their lives out at sea, inhabiting coastlines.
Let's take a look at some of the most popular types of sea birds:
We know of about 18 penguin species, most of which are found in the Earth's southern hemisphere.
Galapagos penguins are the exception, as they live in tropical regions.
The emperor penguin is the one you are probably most familiar with (thanks, Happy Feet).
This penguin spends its life in the Antarctic.
Terns and Gulls
Terns and gulls are very similar species in many ways, as they both hunt in the open sea when not breeding on offshore islands or coastal shores. While gulls inhabit every continent on Earth, terns inhabit every continent except for Antarctica.
One way to tell the difference between a tern and a gull is to look at their wings. Gulls have more rounded wings, while terns have sharper, more angular wings.
Similar to terns, you can find pelicans on every continent except Antarctica.
We currently know of eight living pelican species.
While some pelicans migrate to warm climates during mating season, some remain on the same coasts throughout the year.
Petrels are a pelagic family of birds, meaning most of their time is spent on the open sea. The only reason they return to the land is to breed.
You can find petrels in all oceans around the world, though most petrel species are found north of New Zealand.
The four main petrel groups include gadflies, fulmarine petrels, shearwaters, and prions.
Deep Ocean Animals
Pretend you're in a submarine. You've finally reached the depths of the oceans called the Mariana trench, a place where light is no longer able to penetrate through the water. You look outside and see nothing but pitch black. The pressure of the water surrounding you, along with the freezing cold temperatures, makes this environment seem unlivable.
However, you begin to notice small flashes of light that barely penetrate the darkness. These flashes of light come from bioluminescence, a special trait that allows deep-sea animals to live in the shadowy deep seas.
Some of the most popular deep-sea creatures include oarfish, coelacanth, gulper eel, fangtooth, anglerfish, snipe eel, lanternfish, and nautilus.
What makes these species so unique is that they are able to live in extremely harsh conditions. There are hundreds of bars of pressure, extreme cold (between 3 and 10 degrees Celsius), very little food, no sunlight, and a small amount of oxygen. Many deep-sea creatures must rely on food that floats down from above.
Humans have only explored less than 4% of the ocean floor. With every dive, deep sea explorers discover more new species.
Unfortunately, about one-third of the ocean's animals are currently endangered, according to the IUCN. Some of the most well-known endangered species include:
One of the biggest threats to animals in the ocean is pollution.
More than a million sea animals die each year
due to trash and other types of debris that are left in the ocean by humans. Sadly, some ocean animals have already gone extinct within the past 100 years.
Scary Animals In The Ocean
Though the ocean is a beautiful and diverse environment, it is also incredibly dangerous. While we could write a book on the many dangerous animals found in the ocean, let's talk about some of the most popular species: