When you drop the egg in the water, it fizzes and changes the color of the water. After the dino "hatches" it floats to the surface of the water for your little one to play with.
We had a ton of fun with this egg, but I must recommend that it is only used for kids over 3 years of age or with parental supervision. Youngest used it and he is almost two, but the dinosaur is a choking hazard. It is very tiny once it hatches.