The 15 Biggest Deep-Sea Creatures Swimming Through Our Oceans

The vast array of organisms in the deep sea remains a mystery to humans. Now, marine biologists can add one more puzzle to the list. A collection of odd materials was discovered nearly four miles beneath the ocean surface off the coast of Japan. The strange structures appeared to be small, black, gelatinous, and egg-shaped. The alien-looking masses were documented via remotely operated vehicles traveling along abysmal plains. DNA analysis confirmed that the tiny globules are worm embryos from an unknown species. Though further exploration is needed, discovering such novel marine organisms reminds us of the mysteries beneath the Earth’s deep dark waters.

Though the newly discovered worm eggs are exceedingly small, the ocean is also home to enormous animals of breathtaking proportions. This phenomenon of gigantism occurs because larger animals are more efficient in the depth of the seas than smaller ones. These creatures can navigate long distances quickly to find mates, store more energy for longer periods of time, and adjust to a slow metabolism due to the cold temperatures at the bottom of the ocean. Animals with slower metabolisms grow and mature very slowly and can end up reaching enormous sizes. We’ve compiled a list of the Earth’s largest ocean animals, which we’ve ranked by weight.Read on to discover the 15 biggest deep-sea creatures.

This post was updated on July 17, 2025 to include information on newly discovered worm eggs in the deep sea.

15. Ocean Sunfish

• Average Weight: up to 4,400 pounds

• Average Length: up to 11 feet

The Mola Mola, or Ocean Sunfish, are slow-moving, huge oval-shaped sea creatures. Mostly solitary creatures, they are one of the heaviest bony fish in the world.

14. Giant Ocean Manta Ray

• Average Weight: up to 5,300 pounds

• Average Length: up to 23 feet

The world’s largest ray, the Giant Ocean Manta Ray has a large diamond-shaped body with expansive wing spans.

13. Basking Shark

• Average Weight: up to 11,000 pounds

• Average Length: up to 39 feet

They may look large and threatening, but basking sharks feed on plankton and other tiny crustaceans.

12. Killer Whale

• Average Weight: up to 15,000 pounds

• Average Length: up to 26 feet

Orcas, also known as killer whales, are not whales despite their name but are the largest dolphin species.

11. Minke Whale

• Average Weight: up to 20,000 pounds

• Average Length: up to 35 feet

Minke whales are the smallest members of the Baleen whale family.

10. Whale Shark

• Average Weight: up to 41,000 pounds

• Average Length: up to 33 feet

Whale sharks are the largest fish on our list. These massive sea creatures have mouths that can stretch up to four feet wide.

9. Bryde’s Whale

• Average Weight: up to 44,000 pounds

• Average Length: up to 59 feet

Bryde’s whales are known for their slender, smoky gray-colored bodies.

8. Sei Whale

• Average Weight: up to 62,000 pounds

• Average Length: up to 64 feet

Unusual in the animal world, female sei whales are typically larger than males. Sei whales are a mysterious species with unpredictable movement patterns and it’s not known where they breed.

7. Gray Whale

• Average Weight: up to 72,000 pounds

• Average Length: up to 50 feet

One of the best spots to see the majestic gray whale is during the annual gray whale migration that occurs along the California coast. These big deep sea creatures are filter feeders, eating over one ton of tiny crustaceans per day.

6. Humpback Whale

• Average Weight: up to 80,000 pounds

• Average Length: up to 60 feet

Humpback whales can be found in oceans around the world. They were once threatened by the whaling industry, but their population has made a comeback thanks to conservation efforts.

5. Sperm Whale

• Average Weight: up to 90,000 pounds

• Average Length: up to 59 feet

These big creatures can be found in oceans around the world. Sperm whales are highly social, living in bonded groups that last their entire lifetimes.

4. Right Whale

• Average Weight: up to 140,000 pounds

• Average Length: up to 52 feet

There are three species of right whales: the North Pacific, North Atlantic, and Southern right whale. Sadly, the North Atlantic right whale is an endangered species, with only 360 individuals estimated to remain alive today.

3. Fin Whale

• Average Weight: up to 160,000 pounds

• Average Length: up to 85 feet

Fin whales swim in groups and can often be seen feeding in large groups of many species of whales. They tend to live in deep waters, migrating north in the summer.

2. Bowhead Whale

• Average Weight: up to 200,000 pounds

• Average Length: up to 62 feet

Bowhead whales live in very cold waters in the Arctic and subarctic. Amazingly, bowhead whales may live for 200 years or more, making them the longest-living mammals on Earth.

1. Blue Whale

• Average Weight: up to 352,000 pounds

• Average Length: up to 100 feet

The tongue of this enormous sea creature can weigh as much as an elephant. But despite its large size, the blue whale is not a frightening predator but feeds mostly on krill (tiny shrimp-like crustaceans) which it strains through its baleen palettes. The commercial whaling industry critically damaged the blue whale population, and today they are an endangered species.

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