The dolphins were a stand-in for rational, scientific thinking, but chosen for a reason. And here's a very good indication of it -- an astonishing example of a group of dolphins clearly showing the ability to develop a solution to a problem:
If you were stranded on a deserted island with no materials, would you have the smarts to devise such a strategy? I'm not sure I would.
Someone on a blog somewhere made a point that has stuck with me: if we found evidence of a group of beings on another planet that were as intelligent as dolphins (or pigs, or dogs, or just about any animal), or just these animals themselves, we would be astonished, and revere and protect them. But given the same organisms here on earth, we abuse them in every way imaginable. That's really made me think.