Imagine that you're a football (aka soccer) player. And of course all your teammates are football players too. To communicate explicitly on the football pitch, you use a combination of names, pronouns, short phrases, hand gestures, head movements, etc. But actually most of the communication on the pitch is implicit--players observing each other, inferring the mental state of each other, and making changes based on th…
Just because dolphins possess a possible capacity for language doesn't mean that any language exists.
I'd figure the mutlitude of dolphins in the wild all establish personal colloquial parlances, organized according to the whims an experiences of each individual pod.
Kind of like in that movie Nell, where the children grew up learning to make noises like their stroke-afflicted mother. If there are no regimented social constraints to enforce teaching and learning, wild animals have no externalized motive for establishing the codified norms of a symbolic language.