A symmetrical blade is symmetric about the shaft—both sides of the blade have the same shape. Because it does not matter which direction you hold them, these blades are easier to use and work well for beginners or for less strenuous paddling. White-water paddlers usually use symmetrical blades.
An asymmetrical blade is not symmetric about the shaft—one side of the blade has a different shape than the other side. Because kayak paddles strike the water at a shallow angle, the asymmetric shape lowers the blade deeper into the water and provides additional power and maneuverability. Touring paddlers usually use asymmetrical blades.