Extra Credit: The Strange Density of Ice

Today in class we talked about how it is strange that the density of water actually becomes lower after a certain point (4 degrees C).  Most substances get denser and denser until they freeze.  What would the world be like if ice became more dense as it froze?  Write 2 or more paragraphs describing what this strange world would look like.  (Keep in mind that there is no set answer to this question, so I will be looking for reasonable arguments.)