Often they will swim with each other in synchrony. The pods provide dolphins with social interaction, the ability to herd fish for feeding and make it possible to fend off their only predator, sharks. They gang up on sharks and kill them by ramming the shark's gills with their snout. Some animals develop special senses depending on their environment and the biological niche which they occupy. Anyone who has a dog knows that smell plays a much more important part in their lives than it does in that of humans.
Sight is our most important sense.
Humans, unlike many animals, are able to see in color. However, suppose your biological niche is night time hunting, like dolphins. Reliance on sight would present a problem. It is generally believed that the dolphin's biosonar sounds are produced by nasal sacks located behind the melon, which is the rounded, flexible area of the dolphins forehead filled with an oily substance. A parabolic bony structure called the acoustic shield is located behind the melon as a reflector.