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Aquatic Animals: An Introduction

Last updated date: 20th Mar 2023
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Aquatic animals are those that live in or around water. Freshwater animals are aquatic organisms that populate ponds, rivers, and lakes. Marine or saltwater animals are aquatic species that inhabit oceans. Aquatic animals include both vertebrates and invertebrates.

Do you know how you fantasise about the soft, white sand of tropical islands when you're planning your winter vacation? It's the poop that parrotfish produce after eating coral.

As the largest animal on the planet, a full-grown blue whale's tongue can weigh more than an entire elephant, which means it can weigh more than 7,000 kilograms. Also, shark teeth are actually scales rather than teeth. As a result, if they ever lose a tooth, it will simply regrow. The world inside the water is very interesting. Let's dive deep into their world, and get to know about their habitat and the different characteristics of these animals.

What are Aquatic Animals?

Organisms that live in water and fully depend on water for nutrition are known as aquatic animals. Water contains dissolved oxygen that is used by these animals in the respiration process. Aquatic animals depend on water and cannot survive on land. The salinity of water affects the types of animals that live there. Water has special features, such as: 

  • Temperature variations lower the chance of dryness out instead of getting too hot or cold.

  • Nutrients are easily dissolved and accessible.

  • Aquatic organisms' hazardous metabolic wastes are neutralised and diffused. Aquaculture is the practice of producing freshwater and marine fish in ponds and underwater cages.

Water temperature, photosynthetic access, available oxygen level, and nutrient availability are all characteristics that limit life at various depths in aquatic life zones. As one goes deeper, the temperature drops. Slight variations in temperature can have a big impact on aquatic animals' stability and efficiency.

Aquatic Animals’ Features

Aquatic animals live in water and adapt to their surroundings in order to survive. Adaptation increases the chances of an organism's survival. In various fish, the swim bladder is an air-filled pouch beneath the vertebral column that aids in floating. Ectothermic organisms are those that modify their body temperature in response to variations in water temperature. Blubber aids in the thermal regulation of aquatic species.

Aquatic species have the following characteristics: 

  • The majority of their species live in water, although some do live on land as well.

  • They have paired and unpaired fins that aid in swimming. 

  • Their limbs are either webbed or transformed into paddles for swimming. 

  • Their bones are light and spongy, and their body structure is streamlined. 

  • A thin snout is formed by modifying the skull.

  • The neck is slimmer, and the external ears have vanished.

Saltwater fish excrete a small amount of salt. Freshwater fish have higher salt concentrations in their bodily fluids than those in the surrounding water. Fish have gills instead of lungs. Capillaries were found in the gills, which absorbed dissolved oxygen and released carbon dioxide. A fish's lateral line is a network of neurons that detects water vibrations and motion and aids in keeping the fish moving. Barbels are specialised structures found on fish, such as catfish that increase the creature's sensation of touch. Aquatic animals such as fishes have streamlined bodies that help them swim in the water flow. Fins help in the locomotion of fishes. 

Type of Aquatic Animals

Plankton, nekton, and benthos are types of aquatic animals. The aquatic life zone is dominated by plankton, with feeble swimming and free swimming. Plankton refers to microscopic organisms that swim and float in ocean waters. Fish, turtles, and whales are examples of nekton, which are strong swimming organisms. Benthos are underside decomposers that degrade organic substances found in the dead bodies and waste of aquatic species such as barnacles, oysters, and lobsters.

Aquatic Animals’ List

Dinoflagellates, diatoms, brown algae, red algae, green algae, and seaweed are aquatic species. All aquatic animals include fish, lobsters, dolphins, jellyfish, sharks, sea turtles, starfish, crabs, octopus, whales, seahorses, squid, swordfish, shrimp, killer whales, manta rays, otters, and oysters.

List of Aquatic Animals

List of Aquatic Animals

Aquatic Fauna

“Fauna” is a word for animal life, while “aquatic” denotes water. Aquatic fauna means the animals that are living in water as their habitats. Fish, octopuses, crabs, whales etcare aquatic fauna. 

Interesting Facts about Aquatic Animals

Here are some interesting facts about these animals:

  • Crabs taste food with their feet.

  • Some shrimp species live in symbiotic relationships with fish and corals. In exchange for food, they clean parasites from fish's mouths and protect corals

  • Dolphins sleep with only half of their brain and one eye closed at a time.

  • Angelfish choose their partners for life. If one of them dies, the other will not breed with any other mate for the rest of their lives.

  • Seahorses are the only animals in which the male gives birth and cares for the young.


Water has many features that help in sustainability for animals. Any animal, whether invertebrate or vertebrate, that spends the majority or all of its life in water is considered an aquatic animal. Aquatic animals include benthos, nekton, and plankton. Plankton, which has poor swimming abilities and free swimming, dominates the aquatic life zone. This article gives insight into the life and various adaptations of aquatic animals. 

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FAQs on Aquatic Animals

1. When compared to terrestrial species, how do aquatic animals conserve energy?

Aquatic animals are a type of ectotherm that regulate their body temperature according to the environment. Their body temperature is equal to that of their surroundings, so these animals do not require any energy to maintain their body temperature. There is no energy spent on fighting gravity because their body density is comparable to that of their surroundings. 

For searching for food, animals require extra features that need more energy. All the nutrients are dissolved in water, so the amount of time spent looking for food is reduced, which saves energy. These animals have high feed conversion efficiency, rapid expansion, and the ability to immerse themselves in a multi-dimensional world.

2. What role do aquatic animals play?

Aquatic animals play an important role in the world's most complex ecology. They eat what is left or sick in the water to feed us. The remains in the sea and ocean are used as food by some decomposers. They fertilise and occasionally look after the plants that produce oxygen and filter water. Your entire life is historically derivable from aquatic species. 

These aquatic animals are used in aquaporin for decoration. There are few aquatic animals such as diatom algae that are useful. For example, diatoms that give diatomaceous earth after death are used in polishing and oil filtration. Fish, crabs, octopuses etc., are used and consumed as food in different localities.

3. What are the many types of aquatic habitats?

Aqua refers to water, while habitat refers to a living organism's home. Aquatic habitat is a type of ecosystem that lives in water. Aquatic ecosystems are groups of animals that are interconnected and reliant on one another and their environment. Oceans, lakes, ponds, rivers, and streams are the basic aquatic environments. Marine ecosystems and freshwater ecosystems are the two main types of aquatic ecosystems.

The third type of ecosystem can be found in both freshwater and marine environments. The conditions of the ocean and freshwater systems are largely consistent throughout the year. Since the salt dissolved in marine settings keeps the water from freezing, freshwater ecosystems such as lakes, ponds, and rivers are more prone to freezing over in the winter.