Koi seem to have their own way of swimming as studied and described in this research by Wu, Yang and Zeng.  If you are into kinematics and hydrodynamics this is the reseach paper for you.
 
"Koi carps frequently swim in burst-and-coast style, which consists of a burst phase and a coast phase. We quantify the swimming kinematics and the flow patterns generated by the carps in burst-and-coast swimming. In the burst phase, the carps burst in two modes: in the first, the tail beats for at least one cycle (multiple tail-beat mode); in the second, the tail beats for only a half-cycle (half tail-beat mode)...."
 
https://journals.biologists.com/jeb/article/210/12/2181/16867/Kinematics...