You might guess that candy would sink if you dropped it in the bathtub. (Say, what are you doing eating candy in the tub?) But not all candy sinks. It depends on what's inside the candy.
If something is more dense than water, it sinks. Hershey Kisses will sink, but a 3 Musketeers bar will not. Why not? It contains trapped air (there are air bubbles in that nougat), so it's less dense than water.
You can do this density test yourself on a variety of candies. Marshmallows, including Marshmallow Peeps, will float. Kit Kat bars also will float. Can you find others?
What you need:
Various candies, such as 3 Musketeers bars, Kit Kat bars, marshmallows, chocolate kisses, chocolate pretzels, hard candies, conversation hearts, candy corn, peanut butter cups, and gummi bears
Cups or bowls of water
What to do:
Drop the candy in the water.
Watch what happens: Does it sink or float?
If you have a 3 Musketeers bar, poke it to break the chocolate shell. Do you see bubbles escaping?