3 AA batteries.

The Fisher-Price Seahorse is a proud product of the Fisher-Price Toy Company. The Fisher-Price seahorse design is not complicated, but it is deeply loved by mothers and babies. The Fisher-Price Little Seahorse is actually a toy to soothe children to sleep. It has only two functions, one is to play music; the other is to emit dark light. Unlike other toys, the music of Fisher-Price Little Seahorse is classical music with the gurgling sea water, and the light is very soft and will gradually go out, so the baby will fall asleep.