Synonyms for Buoyant (same or very similar meaning)
WordNet sense 1 (tending to float on a liquid or rise in air or gas):
floatyWordNet sense 2 (characterized by liveliness and lightheartedness):
perky, chirpyWordNet sense 3 (being full of or promoting cheer; having or showing good spirits):
cheerfulFrom the ODE community, based on WordNetadd/edit