In a liquid, objects denser than the liquid (such as rocks) tend to sink, while objects less dense than the liquid (such as inflatable rafts) tend to rise. How does this relate to the observed motions of the liquid in the beaker

If an object weighs more than the weight of the fluid placed in it it will sink. Then floating, which is directly related to the weight or density of the fluid. A more dense, or heavier fluid is capable of "floating" heavy objects.
Proper floating object should be completely above the liquid surface. All floating objects must have some trapped air and this is the only reason they float. The amount of liquid that an object floats on is important in some way,
The density of an object determines whether it floats or sinks to another material. An object floats if it is less dense than the liquid contained in it. If an object is thicker than the liquid in which it is placed it will sink.
If the density of an object in the fluid is greater than the density. Liquid, the object sinks. If the density is lower than the liquid, the object will float up as the fluid is produced.
The product of the density of the liquid volume during acceleration due to gravity is light energy. Therefore, increasing the density of the fluid increases the light energy.