I don't remember if Poser installs a shark or not if not search the freestuff for one. Then it's a matter of seperating the dorsal fin from the body. Use the grouping tool to select it then create a new prop. Size and parent to the kids chest. You may have to make a new template for it so you can match body textures. you might be able to fake the gills by using the fins from daz's anglefish.

I must remember to remember what it was I had to remember.