You may not want a story that involves them directly this early in the saga. However, I might introduce some elements based on their activities during another story if you want.
As you are the animal when in your heartbeast, I consider that you can communicate just as they can. So yes, you will be able to speak to other dolphins. The one caveat is that, as animals, they will communicate at that level. Simple talk of food, predators, etc.
Do you want something that involves you magical animal companion? He's been there since you all arrived to the island, and I'm not sure how often Japik would have checked on him.
Japik could also go around the island looking for sunk ships or other noteworthy features of the sea bed (like the copper discs he found in the Underwater Explorations thread). I'm just wondering the kind of stories you'd want that to lead to, as much of those activities don't involve much in the way of actual interactions.