Just pour some blue tinted clear soap base into a mold 1/4 inch from the top of the mold. Allow to form a skin . Set a rubber duck on film and pour more soap to the top of mold. Pouing in two steps like this gives the duck something to set on. If you just pour once and but the ducks on the still liquid soap, they will sink to the bottom.
Here is an example of colder weather setting in. The white soap base looks like ice!
With peppermint fragrance, this will be great for Christmas presents. Diana