The difference between human and dolphin brains
There are strong possibilities that cetaceans can project an auditory image that replicates a sonar message that they may receive. So a dolphin wishing to convey an image of a fish to another dolphin can literally send the image of the fish to the other animal – it’s similar to a Star Wars hologram, or sending an image via Facebook Messenger.
Even with sleep cycles, cetaceans do it differently. Captive dolphins have been observed to allow half their brain to sleep at any given time, whilst the other part will stay wide awake and aware. This is likely due to the ocean environment – with few places to hide this keeps the dolphins aware at all times. Cetaceans are also considered to be incredible planners