The Drag Equation

All swimming drag follows the formula: drag force equals 0.5 times the drag coefficient times water density times frontal area times velocity squared.

Swimmers cannot change water density. They can reduce frontal area through streamlined posture, lower the drag coefficient through smooth surfaces and technique, but velocity squared is the killer. Faster swimming produces exponentially more drag. This is why the first length of a 200-meter race looks easy and the final length looks like agony — the swimmer is fighting physics that punishes every extra fraction of speed.