What does social comparison theory propose?

Social comparison theory was first proposed in 1954 by psychologist Leon Festinger and suggested that people have an innate drive to evaluate themselves, often in comparison to others. ... She may also compare her abilities to those of students who play other instruments as well

That people have an innate drive to evaluate themselves, often in comparison to others.

they float because they are less dense than the water itself

something denser than water, like a rock, will sink to the bottom