Physics of Scuba Diving
Diver with sea snakeBuoyancy is what determines whether an object will float or sink when it is put into water. Something that is less dense than water will float, while something that is more dense than water will sink.

You can figure out the density of an object by taking that object's mass and dividing it by its volume. Fresh water has a density of 1 (gram/cubic centimeter), while salt water is slightly more dense.

DiverWhen scuba divers go underwater, they want to become neutrally buoyant, which means they are neither sinking nor floating.

Divers are able to acheive neutral buoyancy using two devices:
  • Weight Belt. Divers use a very dense weight belt to help counteract their natural tendency to float.

  • Buoyancy Compensator (BC). A device that can add air if needed to help make the diver more buoyant.

  • It is very important for a diver to reach neutral buoyancy. If they are not dense enough, they will rise back to the surface. If they are too dense, they will fall to the ocean floor, possibly crushing things like fragile coral reefs in the process.
    All images courtesy Corbis Stock Photography. Created in 2003 by David Baxter & Timothy Schmidt.