Why is it said that sound is very important for animals living in water?

               For a long time, it was believed that oceans were silent places. But, as science advanced, it was proved that most of the animals living in waters cannot survive without sounds. 

               We know for a fact that light reaches only till the surface of water. In the case of smell, it fails to spread far from their source, while under water. Contrary to this, sound waves find their ideal medium in water, and travel faster than in air. They move greater distances, and at the surface of water, get reflected back into the depths. That is why even the sound of surf crashing on to a rocky beach travels far into the ocean.

               In general, sounds help most marine animals to sense their surroundings, communicate, locate food, and protect themselves.

               Mammals like whales, for instance, identify objects like food and obstacles using low frequency pulse signals. Dolphins communicate through clicks and whistles. They use the technique of echolocation to detect and characterize objects.