Eye of the Dolphin by M.J. Taormina

Ariel is a unique child. With a disability no one quite understands, she has trouble communicating with her parents, Johnny and Christa. In a desperate effort to better understand her, Ariel's parents take her to Dolphin House, a research facility in Mexico. There, Dr. Kenneth Barnhill puts Ariel in direct contact with a pod of dolphins. They find that despite her trouble with other humans, Ariel has a powerful, immediate connection to the dolphins. Johnny and Christa watch Ariel's world grow, but when disaster strikes Dolphin House, they learn that the situation is far more dire than they dared to imagine.