[S0122017]

I remember also about a case, where dolphins that where trained to do a trick where separated in a basin from other dolphins that hadn't learned the trick yet.

They where visually separated but could still hear eachother. Now, next day the trainers came back to train the other batch and imagine their surprise when they found out that the other group already knew the trick!

Only explanation is that they must have told eachother about what they had to do. It is not too far out, considering that they 'shout' at eachother what to do when hunting.

[spetznaz]

Probably the case. As you said, they do communicate pretty well during hunting and thus it wouldn't be too far-fetched to say that they 'discussed' the particulars of the trick with the other dolphins.

I once saw a very coordinated Killer Whale attack (they are technically dolphins not 'whales'), and the intricacy of the whole thing required a high level of communication.