I should have put it here rather than Miscellany, this is more appropriate.
Obviously there is a problem of anthropomorphizing in interpreting the behavior of another being..but we can't really imagine what an alien's thought processes might be like so have to sort of go with what we know. But clearly the dolphin was cooperating in this case.
I am lucky enough to live where there is a very stable, and in many ways protected, population of Atlantic bottlenose dolphins. I have seen them show off for audiences, race our boat, and come out of the water to a person in our boat to see if we had some mullet for it.
Look at this video of a dolphin playing with a cat...I have been to that park