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10 Underwater Animals

Welcome to 10 Underwater Animals.

Larger than life and often feared, many underwater animals have been legendary throughout history. You may wonder which are the top 10 giant underwater animals. 

We have compiled list of the World’s 10 Biggest Underwater animals (that we know of) for you to enjoy.

From the giant squid that is said to lurk in the ocean’s depths to the massive blue whale, these creatures have fascinated and terrified people in equal measure.


However, our understanding of these animals has increased dramatically in recent years, thanks to technological advances and our ability to explore the ocean’s depths.

The giant squid is perhaps the most famous big underwater animal. For centuries, stories have circulated of a giant creature that drags sailors to their doom. While the reality is probably not quite dramatic, the giant squid is still impressive. 

Growing up to 60 feet long, it is perhaps the giant invertebrate on the planet.

You may have heard the tales of enormous ocean creatures like blue whales, which can grow up to 100 feet long and weigh over 200 tons – making them more than twice as heavy as an average car!

Notwithstanding their size, they are delicate goliaths and are often seen swimming calmly close to more modest whales and dolphins.

They live at depths where sunlight doesn’t reach, so their skin turns bluish-green. These gigantic creatures eat small fish, including some commercially valuable types, such as turbot or tuna, which means less seafood is available for humans who want tasty dishes prepared.

Whale Shark underwater

One more goliath of the profound is the whale shark. The biggest fish on the planet can grow up to 60 feet long and weigh as much as 20 tons. They are channel feeders, and their diet includes predominantly microscopic fish and little fish.

This highlighted some of the most significant underwater animals discovered recently. As technology improves, we will likely find even more impressive creatures in the ocean’s depths. 

Who knows what other discoveries are in store for us?

Importance of Underwater Animals

scuba diving

Oceans are home to the giant, most impressive animals on Earth. Whales, dolphins, and sharks are a few massive animals that have marked the ocean and seas as their territory. 

These creatures play an essential part in keeping up with the healthy ecosystem of the ocean. For example, whales help to keep the water clean by eating large quantities of small fish. 

Also, they help control the population of smaller fish, which can otherwise become overabundant and damage the coral reef. 

In addition, these animals also help to fertilize the ocean with their waste. Their droppings contain essential nutrients for plant life and help support the food chain. 

Types of Underwater Animals

blue whale endangered

There are many different types of underwater animals, each with unique features. Some of the biggest and most popular underwater animals include whales, dolphins, sharks, and turtles. Yes, you heard me right, turtles too. 

  • Whales

Whales are the largest animals on earth; they live entirely in the water and are among the top 10 most giant underwater animals. They are mammals, and they breathe air through their blowholes. Whales eat various foods, including fish, squid, and krill.

  • Dolphins

Dolphins are smaller than whales but still pretty big. They are also mammals, and they live in the water. Dolphins breathe through their blowholes and eat fish.

  • Sharks

Sharks are considered among the most dangerous underwater animals on the planet. They live in the water, and they breathe through their gills. Sharks are carnivores and eat fish, squid, and other animals.

  • Turtles

Turtles are another type of sizable underwater animal. They are reptiles, and they breathe air through their lungs. Turtles eat various foods, including plants, fish, and insects.

  • Giant Crabs

Giant crabs are one of the biggest animals found in the oceans. They are scavengers and will eat just about anything they can find. These predators are hunters who would hunt and kill smaller animals to make them their meals. 

Here are the top 10 biggest underwater animals, based on their average size: 

Biggest Underwater AnimalsSize in FeetSize in MetersWeighed
Lion’s Mane Jellyfish120 Feet 36.6 Meters200 Pounds
Blue Whale108.27 Feet33 Meters200,000 to 300,000 Pounds
Sperm Whale60 Feet18 Meters90 000 Pounds
Whale Shark39 Feet12 Meters30,000 Pounds
Basking Shark22-29 Feet6.7-8.8 Meters10,000 Pounds
Giant Squid43 Feet13.1 Meters606 Pounds  for females and 330 Pounds for males 
Giant Pacific OctopusRadial Spread – 16 Feet 4.9 Meters600 Pounds
Oarfish 36 Feet11 Meters600 Pounds
Ocean Sunfish10.82 Feet3.2 Meter500 Pounds
Japanese Spider CrabLeg Span – 12.14 Feet3.8 Meter40 Pounds

Starting at number 1 on the list of the massive creatures in the world’s oceans.

#1 Lion’s Mane Jellyfish

YouTube video

The lion’s mane jellyfish is at the top 10 biggest underwater animals with the longest tentacles. 

The lion’s mane jellyfish has a long, flowing mane similar to a lion. These beauties are usually seen in calm waters. 

Still, they have been known to live far away from the ocean floor, where they’re occasionally tangled up with marine debris or other tentacled creatures.

As if such appendages weren’t enough already (120 feet worth!), these sluggish swimmers also possess poison-equipped tentacles making excellent traps.

#2 The Blue Whale

sri lanka blue whale safari

Blue whales are marine mammals belonging to the Mysticeti Parvorder and one of the largest known animals to have lived. 

They can be shades of gray or darker on top and lighter underneath, with a bluish tinge throughout their bodies that give them their name!

At least three distinct subspecies of blue whales, each adapted to a different oceanic environment. The blue whale is a baleen whale that filters small crustaceans from the water for food instead of hunting for larger prey. 

#3 Sperm Whale


The sperm whale is a large, toothed animal with an enormous head and small fin. Growing up to 18 meters in length!

The females have the same features, but less than half of them will usually reach this size class because it’s uncommon for males to get here due to their high mortality rate. 

These magnificent creatures live worldwide, oceans preferring deep waters where they’re found primarily alone despite being social animals. 

They communicate using clicks/whistles, among other sounds that are audible even at close range, making themselves heard by sending loud booming blows.

#4 Whale Shark

Surprised divers with whale sharks.

The whale shark is a fascinating underwater animal. It’s recorded as the biggest fish on the planet, growing up to 39 feet long.

Found in tropical waters around the globe, whale sharks have been known to swim alongside humans for long periods. 

Although they are called sharks, they are harmless to people and feed on plankton. Whale sharks are gray with white spots and have broad, flat heads. 

Whale sharks’ mouths can open four feet wide, and their gills are at the back of their heads. They are filter feeders, meaning they strain much water through their gills to catch plankton. 

These captivating animals are a significant part of the marine environment and are essential in keeping the seas healthy.

You might also like to read about our Coral Reef Animals.

#5 Basking Shark

Basking shark

The basking shark is a large, slow-moving filter feeder that is found in the waters of the North Atlantic and Pacific oceans. 

It can grow up to 29 meters in length and is marked amongst the biggest fish on the Earth. The basking shark derives its name from swimming near the water’s surface with its mouth open, filtering small prey items such as plankton and krill. 

Although a harmless creature, the basking shark is often misunderstood as a dangerous predator due to its size and appearance. 

Indeed, this gentle monster represents no danger to people and is a significant piece of the marine environment.

As a top predator, the basking shark helps keep smaller fish populations in check, ensuring that the ecosystem remains balanced.

#6 Giant Squid

YouTube video

The giant squid is the most elusive and mesmerizing underwater animal creature. These giant creatures can grow up to 43 feet in length and weigh 606 pounds for females and 330 pounds for males.

They are believed to live in deep, dark waters around the world and are rarely seen by humans. The size and mystic nature of this underwater animal make it unique. 

These creatures are so large and rare to see that numerous mysteries are yet to unfold. The more I learn about this fantastic creature, the more amazed it leaves me.

#7 Giant Pacific Octopus

YouTube video

The Pacific Giant Octopus is the largest species in its family and can be found across a vast region from Japan to California. They grow up 16 feet long, weighing 600 pounds on average!

Giant Pacific octopuses are intelligent animals known to solve complex puzzles and escape from tight spaces.

They are also excellent hunters and use their eight arms and suction cups to capture prey. Giant Pacific octopuses are famous in the aquarium trade and are a favorite of many divers and underwater photographers. 

#8 Oarfish

YouTube video

The oarfish is a mysterious and little-known creature inhabiting the ocean’s depths. This eel-like creature is the longest bony fish in the world and can grow to lengths of over 36 feet! 

The oarfish is a silver color with long, ribbon-like fins. The oarfish is believed to be a deep-sea creature that rarely comes to the surface, making it difficult for scientists to study. 

While not much is known about the oarfish, it is thought that this creature may be responsible for the legend of the sea serpent.

For centuries, sailors have reported seeing giant serpents in the ocean, and the oarfish may be the creature they have seen. If you’re lucky enough to spot an oarfish, you will have a once-in-a-lifetime experience!

#9 Ocean Sunfish

YouTube video

The Ocean Sunfish is a unique and fascinating creature in open ocean waters. It is the heaviest bony fish in the world and can grow to be over 11 feet long (approximately) and weigh over 500 pounds.

It has a large, flat body, a small, round head, and enormous, rounded dorsal fins. Sunfish have short blunt snouts and sharp teeth. 

They can be any color, but usually silver or brown with blue shades on the bottom part of their body, which gives them an appearance similar to water droplets captured by sunlight overhead!

The Sunfish is a slow swimmer but is a powerful and agile jumper. It is an opportunistic feeder and will eat anything in its mouth, including fish, crustaceans, squid, and even garbage.

It is also known to eat large amounts of jellyfish, which comprise a large part of its diet. The Sunfish is not a threat to humans and is considered a gentle gigantic sea creature.

#10 Japanese Spider Crab

YouTube video

The Japanese Spider Crab is a large and unusual-looking creature found in the deep waters off the coast of Japan.

It is the giant known spider crab, with a leg length of up to 3.8 meters and a body length of up to 40 cm. The crab’s exoskeleton is light orange, with long, thin legs covered in tiny spines. 

The crab is a scavenger and feeds on anything it can find, including dead fish, squid, and shellfish. It is an exciting and unusual animal that humans do not often see.

How to Protect Biggest Underwater Animals?

Beautiful tropical island above and underwater

There are many ways to protect the giant underwater animals. The first thing is to make Marine Protected Areas (MPAs). 

These are the areas where humans have limited activities to safeguard marine life. MPAs can be created by national governments or by international organizations. 

Another way to protect the giant underwater animals is to reduce human-caused pollution. Contamination can emerge from many sources, including processing plants, oil penetrating, and rural overflow. 

Reducing pollution can be done by increasing regulation of polluting industries, developing cleaner technologies, and increasing public awareness of the pollution problem.

Yet another way to protect big underwater animals is to stop overfishing. Overfishing significantly threatens many marine species, especially commercially valuable ones. 

We can reduce overfishing by setting quotas on the number of fish caught, establishing marine reserves where fishing is not allowed, and increasing public awareness of the problem of overfishing.

These actions protect the underwater animals from threats essential to the ocean’s health. Without the underwater animals, the ocean would be a different spot.

Exciting Facts About Underwater Animals

Tiger shark underwater for top 10 ideas to see wildlife

The underwater world is breathtakingly intriguing, where you can find some of the most amazing creatures. There are countless interesting facts about the fascinating underwater animals! For instance, did you know that over 80% of fish live in saltwater?

Another interesting fact is that many animals living in the ocean can change their color. It is because they have cells in their skin called chromatophores. These cells can absorb or reflect light, allowing the animal to change its appearance.

The giant octopus on record weighed more than 600 pounds and measured more than 30 feet across! But the average giant octopus is much smaller, weighing in at around 50 pounds. 

Giant octopuses are expert predators, using their powerful tentacles to eat fish, squid, and crabs for dinner. They are also quite intelligent, with some studies showing they can solve complex puzzles and even use tools.

One interesting fact about underwater animals is that some can produce light. These terrifying creatures control what lives in the oceans. They keep all other animal populations balanced and ensure enough food for them to survive on earth’s Abe colonies! 

These top predators even help maintain water quality by eating tons of plankton every day- without this tiny creature, our seas would be much more hazardous than they currently appear today. 

These beautiful mammals possess an ability called bioluminescence which produces glowing organisms from their bodies when threatened or stressed out. Sometimes, these glowworms can make quite beautiful displays against nights filled with stars above you.

Bottom Line on the 10 Underwater Animals

YouTube video

The oceans are home to various animals, some of which can be seen with the naked eye, while others require an underwater camera. 

There are different types of underwater animals, From the giant whale to the tiny krill that call the ocean home; each creature plays a vital role in the marine ecosystem. 

There’s no way we’ll list them all here (there would be no end). The ocean is a vast and mysterious place, and we are only beginning to understand all its secrets.

If you enjoyed this blog, you might enjoy other ones, such as Best Places for Whale Watching or 10 Best Places to Dive with Hammerhead Sharks.

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