Why does a swimmer feel lighter while swimming?

Answer 1

You feel lighter in water because water is heavier then air and nearly all of you is heavier then air, however when you get into the water parts of you want to float to the surface putting you under the impression that you are lighter.

Answer 2

The water in the pool is much more denser than the air you are constantly exposed to. Because of the fact that it is more dense, it gives more support to your body and basically holds you up.

Answer 3

They are less dense than water. That causes them to float. This makes them feel lighter.