The ocean, that vast body of water that covers over 70% of our planet’s surface, is home to some of the most fascinating and awe-inspiring creatures on Earth. Among them are the giants of the deep, creatures so large they almost defy belief. In this piece, we’ll introduce you to 10 of the largest sea creatures, from massive invertebrates to the colossal whales that roam the ocean’s depths. While some you may have heard of, others might be new to you. Each holds its place in the marine ecosystem, and each is a vital part of our world’s biodiversity.
#10 Leatherback Sea Turtle (Dermochelys coriacea)
Opening our top 10 list is the largest of all living turtles, the leatherback sea turtle. This remarkable reptile can grow up to 7 feet in length and weigh more than 2000 pounds. Unlike other sea turtles, the leatherback doesn’t have a hard bony shell, but rather a tough leathery skin with embedded bony plates. These turtles are true globetrotters, found in oceanic waters all around the world and known for their long migrations between feeding and breeding grounds. Despite their size and widespread presence, they are listed as Vulnerable or Endangered in many areas due to threats like bycatch in fishing gear, habitat loss, and pollution.
#9 Giant Manta Ray (Mobula birostris)
The giant manta ray, with a wingspan that can reach an impressive 29 feet, certainly deserves its spot on this list. These gentle giants have been recorded to weigh up to 5,300 pounds and are easily recognized by their triangular pectoral fins, horn-shaped cephalic fins, large forward-facing mouths, and graceful underwater movements. Manta rays are found in tropical, subtropical, and temperate waters around the world. While they primarily feed on plankton, they are known to visit cleaning stations where small fish remove parasites from their skin. These mesmerizing creatures are considered Vulnerable, with numbers declining due to overfishing and habitat destruction.
#8 Great White Shark (Carcharodon carcharias)
Perhaps one of the most iconic of all sea creatures, the great white shark, can grow to lengths of about 20 feet and weigh up to an impressive 5,000 pounds. Famous for their size and their role in the media as fearsome predators, these sharks are actually quite rare and are considered Vulnerable by the IUCN. They are found in coastal surface waters in every major ocean, and their diet consists of a variety of other marine animals, including fish and seals. While they are at the top of the ocean food chain, great whites are facing increasing challenges from human activities such as hunting for their fins and accidental catches in fishing gear.
#7 Giant Pacific Octopus (Enteroctopus dofleini)
The giant Pacific octopus holds the title of the largest octopus species with an arm span of up to 20 feet and an average weight of around 110 pounds, though some individuals have been recorded to weigh over 600 pounds. This intelligent invertebrate is a master of camouflage and can change both the color and texture of its skin to blend in with its surroundings. Found in the North Pacific from Southern California all the way to Japan, these octopuses are solitary creatures that prefer the cold, nutrient-rich waters. Despite their intimidating size, they have a relatively short lifespan of about 3 to 5 years.
#6 Ocean Sunfish (Mola mola)
The ocean sunfish, or mola, might be one of the oddest-looking fish in the sea, with its flattened body and peculiar fins. Sunfish can grow to be up to 10 feet long and as tall, and weigh nearly 5,100 pounds. This makes them the heaviest known bony fish in the world. They can often be seen basking in the sun near the surface, which helps regulate their body temperature and allows birds to pick off parasites. Predominantly found in temperate and tropical oceans worldwide, their diet mainly consists of jellyfish. Although these creatures are quite large and relatively slow-moving, they are not well studied and their conservation status is uncertain.
#5 Whale Shark (Rhincodon typus)
The whale shark is the largest known fish species in existence. Despite the name “shark” they are harmless to humans, feeding mostly on plankton, krill, and small fishes. These spotted behemoths can reach lengths of up to 62 feet and weigh as much as 47,000 pounds. Whale sharks are found in tropical waters around the world and are known for their gentle nature. Even with their massive size, these sharks are at a high risk due to targeted fishing and bycatch in several countries, leading to their classification as Endangered.
#4 Sperm Whale (Physeter macrocephalus)
Renowned for being the largest toothed predator, as well as having the largest brain of any creature known to have lived on Earth, the sperm whale is truly one of the ocean’s marvels. Males can grow up to 67 feet in length and weigh up to 63 metric tons. They are found in deep waters in all of the world’s oceans and are known to dive as deep as 7,380 feet in search of their preferred prey, squid, and fish. Sperm whales have historically been hunted for their oil and spermaceti, leading to a significant decline in their numbers. They are currently considered Vulnerable to extinction.
#3 Southern Elephant Seal (Mirounga leonina)
The massive southern elephant seal is the largest seal species, with males typically reaching lengths of up to 20 feet and weights of up to 8,800 pounds. These seals are named for their large size and the trunk-like proboscis on the males, which is used to produce loud roaring sounds, especially during the breeding season. They are found in sub-Antarctic and Antarctic waters and spend up to 80% of their lives in the ocean, capable of diving over 4,900 feet deep and holding their breath for more than two hours. While hunted heavily in the past for their blubber, protections have allowed their numbers to recover, and they are now considered of Least Concern in terms of conservation status.
#2 Blue Whale (Balaenoptera musculus)
No list of giant sea creatures would be complete without the blue whale, the largest animal to have ever existed on Earth. These magnificent marine mammals can reach lengths of up to 100 feet and weigh as much as 200 tons. Their tongues alone can weigh as much as an elephant and their hearts, as much as a car. Blue whales are found in all the world’s oceans, save for the icy waters of the Arctic, and primarily feed on tiny shrimp-like animals called krill. Due to intensive whaling in the 20th century, blue whale populations were drastically reduced, and they are now considered Endangered. However, their numbers have been slowly recovering due to international protection.
#1 Antarctic Blue Whale (Balaenoptera musculus ssp. Intermedia)
The Antarctic blue whale, a subspecies of the blue whale, holds the title of the largest creature on the planet. These titans can reach lengths exceeding 98 feet and weigh approximately 400,000 pounds. This specific subspecies, found in the Southern Ocean surrounding Antarctica, is particularly adapted to the icy environment and has a slightly larger body mass and thicker blubber layer than other blue whale subspecies. Feeding almost exclusively on krill, a single adult blue whale can consume up to 4 tons of krill in a day during the feeding season. Like their relatives, Antarctic blue whales were nearly hunted to extinction by the whaling industry but have been slowly recovering since whaling bans were instituted. They remain categorized as Endangered and are the subject of many conservation efforts.
The ocean’s vastness and depth hold mysteries we have yet to uncover and species we have yet to discover. These giants of the deep give us just a glimpse into the incredible array of life beneath the waves and remind us of the importance of preserving our shared global ecosystem. Their size and majesty are unmatched on Earth, and their presence in the ocean is a testament to the remarkable diversity and the capacity of life on our planet.