The 12 Largest Sea Creatures in the World

Written and verified by the biologist Cesar Paul Gonzalez Gonzalez

Last update: 25 June, 2023

The sea is an immense sanctuary that hides incredible secrets in its waters. It contains more biological diversity than anywhere else, and yet only a fraction of its species are currently known to us. It’s able to house creatures of considerable size. Some are quite dangerous to humans, while others are barely noticeable. Stay with us as we reveal the largest sea creatures in the world.

Although some land animals are impressively big, sea creatures far exceed expectations. It’s almost hard to believe that they’re real, as many of them look like they’ve come out of a science fiction movie. Continue reading and get to know some of the titans that live in the seas.

Giant marine animals

The ocean is one of the least explored ecosystems, with its enormous expanse and depth that’s inaccessible to humans. Despite this, we are aware of some incredible animals. If you want to see what nature is capable of, take a look at the following 12 giant sea creatures.

1. Lion’s mane jellyfish (Cyanea capillata)

This is perhaps one of the most amazing animals that the sea can hide, not only for its size, but also for its beautiful appearance. The lion’s mane jellyfish is considered the largest of its group, measuring around 37 meters (121 feet) in length and having a diameter of almost 4 meters (13 feet). It lives in the northern Atlantic Ocean and Arctic Ocean.

2. Sperm whale (Physeter macrocephalus)

The sperm whale is a beautiful cetacean that can travel in almost any ocean in the world, although it prefers the polar regions. It can measure more than 20 meters (65 feet) long and weighs around 50 tons. Its head is quite large and contains within it the spermaceti organ, which acts as a kind of ballast to increase or reduce the animal’s buoyancy.

3. Giant squid (genus Architeuthis)

Giant squid are one of the largest marine creatures and seem to come right out of science fiction. They are capable of measuring 14 meters (46 feet) long on average, but the largest ones are likely to reach 20 meters (65 feet). They have 8 arms and 2 tentacles that contain adhesive suction cups to attach themselves well to surfaces.

4. Whale shark (Rhincodon typus)

Despite its frightening name, the whale shark is a docile filter-feeder. This means that it doesn’t hunt actively like other sharks, but feeds on plankton floating in the water. It’s approximately 12 meters (40 feet) in length, although it looks even bigger when it opens its huge jaw to eat.

5. Basking shark (Cetorhinus Maximus)

The basking shark averages 10 meters (32 feet) in length. It isn’t an active hunter, but a filter feeder. For this reason, it usually swims quite slowly while opening its mouth to grab as much food as possible. It can be seen in areas close to coasts all over the world, but has a preference for regions with cold waters.

6. Killer whale (Orcinus orca)

The killer whale is a cetacean that measures between 7 and 9 meters (23 to 29 feet) long. It’s characterized by a distinctive color pattern, which divides the body with black and white tones. Unlike its relatives – the regular whales – this species has teeth that make it quite efficient as a predator. It has a curious habit of jumping on the surface of the water to warn its conspecifics that it has found food.

7. Giant Pacific octopus (Enteroctopus dofleini)

This invertebrate isn’t only very large, but also one of the longest-lived octopus species, with an average lifespan of 4 years. It’s 9 meters long and weighs about 270 kilograms (600 lbs). Like other species of its kind, it has pigment cells in its skin that change color to blend in with its surroundings.

8. Giant manta ray (Mobula birostris)

The giant manta ray is one of the largest batoids (stingrays and manta rays) in existence. It averages 9 meters (29 feet) wide and weighs just over a ton. Its physical shape is flattened and it looks as if its fins were real wings. It has no stingers on its tail and is quite reclusive, so it doesn’t usually cause conflicts with people.

9. Giant oarfish (Regalecus glesne)

This beautiful fish is one of the largest marine creatures, as specimens with a maximum length of 11 meters (36 feet) have been recorded. It usually lives at depths of 1000 meters (3280 feet), although it also rises to the surface without any problem. It’s believed that these organisms are capable of “predicting” earthquakes. Of course, there’s no evidence that this is true.

10. Largetooth sawfish (Pristis pristis)

The sawfish is characterized by an elongated snout composed of between 14 and 22 “teeth”. It uses this feature to its advantage to detect and cut its food, as it also contains pores that are sensitive to movement. It inhabits the intertropical oceanic regions near Africa, the Caribbean and Australia. Its size reaches a maximum of 5 meters (16 feet).

11. Greenland shark (Somniosus microcephalus)

This species is considered the longest-living vertebrate in the world, living an average of 272 years. It lives at a depth of 2000 meters (over 6500 feet) near the Arctic Ocean, around Greenland and Iceland. These sharks don’t have efficient eyesight, although they’re still efficient and skilled predators.

12. Blue whale (Balaenoptera musculus)

This is known as the largest vertebrate on the planet. The blue whale can reach over 25 meters (82 feet) long and weigh about 180 tons. In fact, its heart alone could equal the size of a small automobile. This species is currently facing serious conservation problems, as its specimens have been hunted without control for years.

As you can see, the sea hides a vast variety of large and impressive marine creatures in its waters. However, these are only the ones known to man, as many other enormous creatures could be lurking in its depths.