Water resists your movement — a lot. Run, as fast as you can, 25 yards in waist deep water and you'll learn all about resistance. You'll learn how real it is.
For swimmers, balance, posture, and alignment minimize resistance.
At least half of swimming is minimizing resistance.
Water has a dual nature. The water under you supports you, if you let it. The water in front of you examines and resists you.
More about water density
