M&Ms and Skittles sink in water--mostly.  To see what floats, try this:

What you need:

• Cup of water
• M&Ms or Skittles
  

What to do:

1. Drop the M&Ms in the water.
   
2. After a few minutes, look for floating letters.  (Do not stir the water--you might break the letters.)

What's happening:
The white letters on M&Ms and Skittles are printed with edible ink that doesn't dissolve in water.  When the rest of the candy shell dissolves, the letters peel off and float. Some of the letters break into pieces, but a few should survive intact.