Buoyancy

Astronauts prepare for spacewalks by practicing their tasks underwater in a giant pool called NASA's Neutral Buoyancy Laboratory.

Many species of fish use an organ called the swim bladder, which is filled with gas, to adjust their buoyancy.

That won't impact the buoyancy?

The buoyancy, vivacity, energy, enthusiasm and ambition ordinarily associated with youth can be maintained through middle age and in some cases even to old age.

There is, besides, something in the appearance and bearing of a midwife upon those occasions which diffuses a spirit of buoyancy and light-heartedness not only through the immediate family, but also through all who may happen to participate in the ceremony, or partake of the good cheer.

A body with negative buoyancy will sink in water.

With how much lighter a step, with how much brighter an eye, did Francesca wander through the forest, even in the last desolation of autumn, than she did in all the bloom and buoyancy of spring!