I think it started with the Plebe class of 2018; the song (released in 2013) started to be played at 2014 football games and cadets adopted it. A parent from the class of 2018 created a Tsunami tshirt in gold and soon a good portion of Plebes were given the shirt by their parents and wearing it under their uniforms at games. I don't remember hearing the song / seeing the jumping at any 2015 games, but it sure did make me smile to see cadets embrace it again at this year's Army/Navy game.
Just found another video from 2018's CFT runback in 2015 where it is played (and cadets are jumping) on the apron. So I'd say it is an unofficial song of the class of 2018.