noun (n)

• cheerfulness that bubbles to the surface(noun.feeling)

  Synonym:
  perkiness
  

  source: wordnet30
• the property of something weightless and insubstantial(noun.attribute)

  Synonym:
  airiness
  

  source: wordnet30
• the tendency to float in water or other liquid(noun.attribute)

  source: wordnet30
• irrepressible liveliness and good spirit(noun.attribute)

  Example:
  I admired his buoyancy and persistent good humor.
  

  Synonym:
  irrepressibility
  

  source: wordnet30
• The property of floating on the surface of a liquid, or in a fluid, as in the atmosphere; specific lightness, which is inversely as the weight compared with that of an equal volume of water.(noun)

  source: webster1913