With a kayak it is not always easy, keeping a straight course. Specifically that applies to side wind, strong waves, drift and water turbulence. 

A boat should always be highly manoeuvrable, to change direction, to give way, to come ashore, and all must function swift and well.

Foot-pedal steering is a great help. Rudder and foot-pedal steering keep the boat on course and enable change of direction.

Steering device