The Goldfish soap in a bag looks like the little fish kids used to bring home in plastic bags from the pet store. The big difference is these ones won’t go belly up in the aquarium and you won’t see them being flushed down the toilet.
What you’re seeing surrounding the fish isn’t water but rather glycerin soap. As the soap gets used up, you come closer to the plastic toy in the middle.
Placing a toy in the middle of a bar of soap is a great idea, perhaps it’ll get younger kids to bathe more. In fact, there is now an incentive to bathe thoroughly to get that toy out as quickly as possible.