BUOYANCY
image courtesy of https://www.shmoop.com/fluids/archimedes-principle.html
When you get certified to SCUBA
dive you learn the importance of controlling your
buoyancy. Keeping yourself neutrally buoyant is
necessary to keep both yourself and the marine
life safe.
Being 'neutrally buoyant' means that the divers
density is equal to the density of the surrounding
water . Which means while breathing
normally, they don't ascend or descend. This
keeps the diver safe because without neutral
buoyancy, they could sink or ascend too fast, and
it keeps the marine life safe because the diver
isn't crashing into the sea floor and damaging
coral.
Archimedes' Principle
explains how buoyancy works. It states that the buoyant
force is equal to the weight of
the water the object displaces.
Divers control their buoyancy with
their Buoyancy Control Device (or BCD) and weight.
(To learn more about the BCD, jump to this page.)
If they want to positively buoyant, they can add
air, and if they want to be negatively buoyant,
they can let some air out.