The Oxford Thesaurus An A-Z Dictionary of Synonyms - buoyant adj.

1) afloat, floating, floatable: The wood was water-logged and no longer buoyant. 2) light, resilient, lively, vivacious, bright, cheerful, carefree, blithe, animated, jaunty, bouncy, ebullient, light-hearted , Colloq peppy: One had to admire his buoyant optimism, even under adverse conditions.