That is why people who snooze or doze briefly while driving a car are known to be suffering from 'dolphin sleep'. The best ability in fresh water dolphins is their echo- location. Both mother and baby recognise each other by emitting supersonic echo-locating waves that return immediately to indicate if the sound was coming from its own baby or from its own mother. As yet no machine or device has been invented that is sensitive enough to catch its frequency. There are far more sensitive devices, but not in this context.
Dolphins can also detect the fishing net and jump over it in time.
The friendly creatures are also very clever and you can't befell them easily. Despite all this, the dolphins have no sense of smell. Since dolphins belong to an intelligent group of animals, it is impossible for them to not communicate. The familiar marine dolphins, that seem to keep a permanent smile on their face, are very vocal, they chatter like a cricket, emit wonderful sounds that spread joviality in the air accompanied with frequent, vigorous, hopping and jumping in the water. Underwater recording has, so far, revealed no sing-song pattern of sound waves in blind dolphins that suggest their using a language.