Answer: buoyant

AnswerCrossword Clue
BUOYANTLighthearted
BUOYANTCheerful
BUOYANTLike a life preserver
BUOYANTTending to float
BUOYANTElated
BUOYANTLike a life jacket
buoyanthaving buoyancy (the tendency to float, also BUOYANCE)
buoyantable to float
buoyantcheerful