Scuba Source

Buoyancy Basics for Scuba Diving

Buoyancy plays a very important role in scuba diving.

Buoyancy principle: An object placed in water is buoyed up by a force equal to the weight of the quantity of water it displaces.

What does this mean? When placed in water, an object will displace a certain volume of water. If an object weighs less than the amount of water it displaces, then it will float (positive buoyancy). If an object weighs more than the amount of water it displaces, then it will sink (negative buoyancy). If an object weighs the same as the amount of water it displaces, then it will neither float nor sink, but will simply remain suspended in the water at the same depth of water (neutral buoyancy).

Think of a large ship made of heavy steel. Even though the ships weighs a lot, it displaces an amount of water that weighs more than itself, so it floats.

Buoyancy is very important in scuba diving. At the surface, positive buoyancy allows you to remain at the surface without a lot effort, like treading water. Underwater, positive buoyancy allows you to rise to a higher depth or to the surface in a controlled manner. Likewise, negative buoyancy allows you to travel from the surface to your desired diving depth in a controlled manner. Once you get there, you establish neutral buoyancy to stay where you are, which gives you a sensation of being weightless.

Two pieces of scuba equipment are very important to your buoyancy. The first is the aptly-named Buoyancy Control Device (BCD), which is a vest that has an air sack that you can inflate and deflate to control your buoyancy. The second piece of equipment is a weight system, which can be either a set of weights integrated into the BCD vest or a separate weight belt.

NOTE: The information on this page is for educational purposes only. You should receive proper training, such as a certification program, before attempting to dive.