I only bring ponchos for Kali because you don't get kind of wet, sorta wet, or even a little soaked. You are head to toe drenched. Even with a poncho I got wet.
Every other water ride (not at an exclusively waterpark place) never gets you that wet. This is like swimming in your clothes. And I think it's a fun ride, but I'd never want to go on it without a) a poncho or b) the ability to change immediately after.