Bubblers are glass pipes that are blown in a certain style to incorporate water as a filtering agent.  Water can cool and clean smoke, in turn making the smoking experience less harsh and more enjoyable.  This is one of the easiest ways to reduce the heat and tar associated with smoking.  Bubblers typically come in a Sherlock or Sidecar style, are still small enough to comfortably fit into your hand and are available in a variety of colors.  Prices usually begin around $50.