The seahorse in dreams is the symbol of magical aspects of your waking life that are not very common. However, these joys will be only for a short period of time. The dream also shows that the miracle is about to happen. Sometimes the seahorse is the reflection of the certain individual who has tender, beautiful qualities just like the seahorse has, therefore this dream simply shows how happy you are being surrounded by this person.
Dream dictionary: Seahorse dream meanings
Seeing it is a symbol of good luck and happiness.