Animals in Ocean

How many animals are in the ocean? How many species do they represent? Scientists estimate that 3.5 trillion fish, marine mammals, and other invertebrates call one of the world’s five oceans home. To date, researchers have identified about 230,000 marine species but believe there could be as many as two million.

Ocean Animal Fun Facts

The most common vertebrate on Earth is the bristlemouth fish, of which there are 32 species. Guesstimates put their population number somewhere between hundreds of trillions to a quadrillion.
Blue whales are the largest animals in the ocean and on the planet. In fact, the 98-foot (that’s two school buses), 190-ton animals are the largest ever known to exist. Females are bigger than males, and the average skull is 19 feet — the size of three refrigerators stacked atop one another! Incredibly, blue whales gain 200 pounds a day in their first year.
The biggest non-mammal fish in the ocean is the whale shark — aka Rhincodon typus. Scientists estimate that the average individual falls somewhere between 46 and 72 feet and lives between 80 and 130 years.
The largest non-shark or non-mammalian ocean dweller is the giant ocean manta ray — aka the Australian devilray, giant manta ray, and devilfish. Despite their motley nicknames, they’re not very dangerous and only eat small fish. The flat, triangular-shaped swimmers can grow up to 30 feet and weigh three tons.

Ocean Animals: Types of Marine Life

Examples of all taxonomic domains — Archaea, Bacteria, and Eukarya — live in the ocean. Typically, scientists divide aquatic wildlife into seven sections:

Shellfish, Cephalopods, and Crustaceans
Corals and Other Invertebrates
Marine Mammals (i.e., whales, dolphins, etc.)
Fishes
Sea Turtles and Reptiles
Seabirds
Sharks and Rays

Endangered Ocean Animals

Due to centuries of over-fishing and pollution, many ocean animals are endangered or on the verge of extinction. A sampling of threatened species include vaquitas, blue whales, Steller sea lions, and Hawksbill sea turtles.

Vaquita: Critically Endangered

Vaquitas, which means “little cow” in Spanish, are Critically Endangered. Scientists believe only a dozen remain in the wild. They’re the smallest cetaceans and only live in the Gulf of California. Currently, their main threat is getting caught up as by-catch. Additionally, since so few remain, reproduction isn’t plentiful.

Blue Whales: Endangered

Blue whales, the largest animals on Earth, are Endangered under IUCN standards. They were almost hunted out of existence in the 19th century, but conservation laws banned all whale hunting by 1967. Today, the animals are struggling to make a comeback. Current population estimates stand at 10,000 to 25,000 individuals.

Steller Sea Lions: Near Threatened

Steller sea lions, which inhabit northern regions of the Pacific Ocean, are Near Threatened. The amphibious marine mammals are smaller than walruses but larger than other sea lion subspecies. Scientists are somewhat stumped as to the species’ sudden and rapid decline. More and more, overfishing looks like the culprit, but the jury is still out.

Hawksbill Sea Turtles: Critically Endangered

Hawksbill sea turtles can be found in all parts of the ocean and attached lagoons. Their colors change slightly depending on water temperature. In the past, the animals were hunted for both their meat and shells, which were used to make tortoiseshell products. Today, even though several laws protect the animals, poaching continues.

Below you can find a complete list of Ocean animals. We currently track 144 animals in the ocean and add more daily!

Ocean Animals FAQ

What Is the Ocean?

Technically, the ocean is one massive aquatic mass that encircles the globe. It’s filled with salt water and makes up 90 percent of the planet’s hydrosphere and 71 percent of the Earth’s surface. Additionally, the ocean holds 97 percent of the planet’s water. Even though the ocean is a continuous unit, we break it into five sections (from largest to smallest):

Pacific Ocean
Atlantic Ocean
Indian Ocean
Southern (Antarctic) Ocean
Arctic Ocean

How Deep Is the Ocean?

Most of the ocean is two miles deep. The deepest point, known as the Mariana Trench, is seven miles deep.

What Is the Difference Between a Sea and Ocean?

Are the words “sea” and “ocean” interchangeable? Not quite. A sea is a body of water that’s partially or fully enclosed by land. An ocean, on the other hand, is a wide-open mass of water.

When Did the Ocean Form?

Currently, scientists age the ocean at 4.6 billion years old. All evidence suggests that it formed during the Hadean geological era and began life as a fiery, bubbling lava pit.

Sea Countries Animals Lists

Click any of the countries below to see a detailed list of animals located in that country!