After reading some information about dolphins, I can confirm that they have a special language. They can communicate each other through sounds which are incomprehensible for humans. These sounds are uttered in an extremely loud volume, ten times louder than human language.
I don’t know exactly how dolphins could help Nikki to speak. But certainly I found a website that speaks about a special center in Japan, Sanuki Dolphin Training Center, where dolphins help children with disabilities. This is the link http://www.bwfilms.com/articles/dolphins.htm. This website explains how therapeutics and doctors came to the center with the children who enter in the water to have interaction with this special kind of mammals.
I also found at Wikipedia information about how dolphins were trained by army to help them especially in tasks like mine the ocean’s depth.
I think dolphins have a special place in the history because they have a particular charisma among the mammals.