Water, Water Everywhere! Marine Biology for Kids

Water, Water Everywhere! Marine Biology for Kids

Nearly 70% of the Earth is covered in water, most of which comprises the world's oceans. The oceans are home to over one million known species of marine plants and animals and many more that scientists say haven't been discovered yet. Marine Biology is the study of these organisms, their behaviors and the environments in which they live. Let's dive into this underwater world and learn more about the ocean and the creatures that inhabit it.

Marine Habitats

The earth's oceans are so vast and diverse in climate, geography, water temperature, and more, that they are divided up into different habitats. These habitats can generally be categorized as either coastal or open ocean habitats. Examples of coastal habitats include shores, estuaries, mangroves, and coral reefs. This is where the majority of marine life can be found due to a greater concentration of nutrients and sunlight. Examples of open ocean habitats include surface waters, deep sea, and sea floor habitats such as trenches and sea mounts.

Marine Habitats

Ocean Habitats for Grades 1-3

Coral Reefs


Fish are cold-blooded animals that live in water. Common characteristics among all fish are that they have backbones, fins, and gills. There are approximately 32,000 different species of fish, the largest class of vertebrates on Earth. Fish can be divided into three major classes: jawless, cartilaginous (sharks and rays), and bony fish. The vast majority of fish are bony fish and can be divided into two categories: ray-finned fish and lobe-finned fish.

Learn About Fish

What Makes a Fish a Fish?

Classification of Fish

Fish FAQ

Marine Mammals

Marine mammals are animals that live in water that, unlike fish, are warm-blooded, breathe their air through lungs, and bear live young. There are five groups of marine mammals: pinnipeds (seals, sea lions, and walruses), cetaceans (whales, dolphins, and porpoises), sea otters, sirenians (dugongs and manatees), and polar bears.

What is a Marine Animal?

Whales and Dolphins for Kids

What's the Difference Between Seals and Sea Lions?

Fun Walrus Facts for Kids


Seabirds are birds that live mostly on or near the ocean. Gulls, terns, skimmers, pelicans, and penguins are all examples of seabirds. They have adapted similarly in order to survive life in the marine environment. Most all seabirds feed in saltwater and have salt glands that aid them in digestion. They also have a strong sense of smell that helps them find food or colonies in the vast ocean.


Facts About Penguins

Seagull Facts


Invertebrates are defined as animals with no backbone. Examples of marine invertebrates include jellyfish, octopus, squid, crabs, lobster, clams, shrimp, starfish, and sea urchins. Invertebrate vary greatly in their physical characteristics. Some animals, like jellyfish, have a fluid-filled, hydrostatic skeleton and others, such as crustaceans, have hard exoskeletons.

Marine Invertebrate List and Pictures

Invertebrate Animal Guide

Octopuses and Squids

Fun Facts About Jellyfish


Reptiles are cold-blooded animals with backbones. Examples of marine reptiles include sea turtles, sea snakes, marine iguanas and saltwater crocodiles. Some marine reptiles barely leave the water while others, such as the sea turtle and crocodile, venture on land to lay their eggs.

Marine Reptiles

Sea Turtles

Crocodiles: Facts and Pictures

Marine Iguana

Plants and Algae

Marine algae, also known as seaweed, can be broken up into three categories: red, green, and brown algae. There are over 6,000 species of red algae, including Irish moss. Red algae can grow in greater ocean depths than green and brown algae. There are over 4,000 species of green algae. They can be found in both freshwater and marine habitats. Brown algae is the largest type of algae and can be found in temperate and arctic climates. Kelp is a common type of brown algae.

What is Seaweed?

Marine Plants: Algae

Giant Kelp Questions


Microorganisms are organisms that are so small they cannot be seen with the naked eye. Marine microorganisms play an important role in the underwater ecosystem, as they provide the foundation for the food chain and help maintain the overall function and health of the ocean. The three most common types of marine microbes include viruses, bacteria, and protists.

Marine Microbiology

Marine Bacteria

What is Plankton?

Learn More!

Ocean and Conservation Resources, Activities, and Videos

What is a Marine Biologist?

Endangered Marine Animals

Written By: Lynn Taylor