What is buoyancy? That’s a question you will hear quite often as a PADI Instructor or Divemaster. We could talk about it in general like Archimedes did, who by the way discovered the principle, but we as divers are only interested in buoyancy related to water.
The straight forward answer what is buoyancy would be; an object wholly or partly immersed in a fluid is buoyed up by a force equal to the weight of the fluid displaced by the object. This was stated by Archimedes back in the old Greece, but have a look at the video to get a better understanding of this statement.
This means the denser the fluid, the more buoyant the object will get. In water; objects in salt water will be more buoyant than the same object in fresh water, but more in detail about the difference in the next chapter.