Littlefoot, Cera, Spike, and Ducky get involved in a brand new musical adventure about the magic of discovery. When a heavy rainfall causes something new and mysterious, Littlefoot decides to explore the Great Valley.

He quickly becomes friends with Mo, a mischievous and playful dolphin who is lost and cannot find his way to the big water. Littlefoot and his prehistoric friends come to help him, cleverly avoiding a terrifying shark, proving the value of courage, friendship, and diversity.