buoyancy

noun

1.
cheerfulness that bubbles to the surface
perkiness
Derived from:
buoyant
2.
the property of something weightless and insubstantial
airiness
Derived from:
buoyant
3.
the tendency to float in water or other liquid
4.
irrepressible liveliness and good spirit
irrepressibility
Derived from:
buoyant