a term to describe a moment when somethin that was once great has reached a point where it will now decline in quality and popularity.

Origin of this phrase comes from a Happy Days episode where the Fonz jumped a shark on waterskis. Thus was labeled the lowest point of the show.

The precise moment when you know a program, band, actor, politician, or other public figure has taken a turn for the worse, gone downhill, become irreversibly bad, is unredeemable, etc.; the moment you realize decay has set in.

Original meaning was the point when a television series shows it has run out of ideas and must resort to stunts to retain viewer interest. Derived from a scene in the last years of Happy Days when the Fonz waterskied over a shark. Includes actions such as "it was all a dream" episodes, live episodes, lead actors playing guest characters, and putting entire cast into a parody of some pop cultural event.

Refers to the specific moment when a TV show goes downhill. From the Happy Days episode where Fonzie overcomes his fear of sharks by jumping over one while wearing water skis.

when something stops getting better and starts getting worse

The precise moment when you know a tv show, rock band, or actor has gone downhill.

Hung around too long. Kept something going when it had obviously run its course or became useless.