Zac Efron -- Shark Rodeo! This Doesn't End Well ... Usually (TMZ TV)

Tiger sharks bite people -- lots of 'em ... a fact Zac Efron either never learned or somehow forgot, since he jumped in the Pacific and hitched a ride on one!!

This is like watching someone's death wish play out -- or maybe it's a pure moment between human and shark ... but we're leaning death wish.