Human-Dolphin Childspeak Learning
Surround a human child with dolphins chat over sound filter to match human hearing, and get the first human naturally learn dolphin.
Humanity is yet to learn dolphin language. Various ways had been tried out by adults, like carrying keyboards with meanings, and going around to interact with them in their natural habitats. However, adults, even equipped with modern computers, are limited in their ability to pick up the subtle relationships that a child's brain would pick up. Human children of early age are able to learn language really rapidly, and they are able to pick up emotional, semantic and cultural cues that adults are insensitive to. Unlike adults, children of early age have a great ability to rapidly combine linguistic elements to determine the relationships between them.
So, one part of this idea would be to use human children to learn dolphin language. However, how would you get one hear what they have to say, and speak back? Even if it seems that dolphin speak is very hard for humans to pronounce or modulate, it is known that some humans are able to mimic sounds of animals really really well. From this, it follows that, if we transform the dolphin sounds to the frequencies of human hearing and speaking, then it is not unlikely that humans (especially kids) will be able to learn to modulate sound to reproduce them (which then can be transformed back to high frequencies for dolphins to hear).
However, how would one get very young kids enter the water with dolphins, when kids are still in their cribs? I guess, the third part of this idea has to be based on a communications terminal, where a child's crib is designed with a first-person-view of a dolphin. Perhaps it could be done using robotic dolphin controlled by the child from a crib, however, a concern is that robotic dolphins may appear very different in ultrasound, so, perhaps a basic submarine with ability control from a baby's crib would be better and less confusing to dolphins... seeing that there is real intelligence (child's mind) behind it, perhaps would make dolphins curious, and explore the communication. Other approach could be having a camera on a real dolphin to provide context to the learning of human child, and then, the ability to talk to that one dolphin, as a companion, or to talk to other dolphins as well (with some accent to distinguish from the natural voice of the dolphin carrying communications equipment). This part is actually, would require further investigation for the best way of doing, to protect both the dolphins and the children within such activity.