Aquatic habitat is one of the most important habitats, where a large number of animals live. The aquatic, habitats include, both freshwater and marine water animals. Aquatic adaptations develop due to an aquatic mode of live animals, like those of fishes, mammals, like the seal, dolphin, whales, etc. 

The structural and functional adaptations of aquatic animals are: 

1. for movement. 

2. for protection of the body. 

3. for feeding. 

4. for obtaining dissolved oxygen. 

5. for remaining buoyant in water, 

6. for balancing the fluctuations, in pressure. 

The aquatic adaptations for aquatic animals to their aquatic life, are as follows: 

1. The body of most of the aquatic animals is streamlined or spindle-shaped. Their body is laterally compressed and offers the least resistance to motion, as the fish swims. 

2. The animals locomote in water by fins (in fishes), flippers (in whales) or, webbed feet (in frogs and ducks), for swimming in water. 

3. The body is covered with waterproof, scales, cuticle, shell and a slippery substance for reducing the surface tension. 

4. Aquatic animals possess the ability to feed in water. 

5. Swim bladder and gills are the main respiratory organs in aquatic animals. Gills have a large surface area, to extract oxygen dissolved in water. In mammals, lungs are the respiratory organ. 

6. Hair, skin glands and oil glands are absent, in aquatic animals. 

7. Aquatic animals are generally larger in size.