I have seen and witnessed this behavior in a pod of porpoises off the
coast of Florida. They were accompanying the ship I was on and seemed to
use this as "communication." They will do this on their own, or in
association with a vessel. I beleive they have been noted doing this
around whales. The conclusion has been they were "playing," yet for some
reason, this is a rather _costly- play behavior in an animal whose body
form, like seals, are adapted to _reducing_ drag. Yet they "frolic,"
"play," etc., in behaviors that _WE_ infer for them based on our own
psychosocial behaviors. This is akin to Freudian inferences for what _we_
would do being put onto another, independant of what they were doing.
Instead, the energetics they exhibit are beyond the need to move make
dolphins and porpoises exceptional to most marine animals, because it
would seem to be an "unneccessary" behavior that contradicts the
conservation and constraints of the evolutionary form. This may speak of
some intelligence. But it also speaks of a behavior that would not seem to
be _neccessary_ for normal locomotion, yet is still performed.