I just started using Kdenlive and while I'm impressed I don't really know how to distort voices, like for example if I want to make a voice echo, or if I want to make a voice sound like it's underwater or something like that. if someone could answer this for me that would be great cause there are no answers online that I could find.

Echo/reverb effects was removed from effects lists due to issues/bugs ... i don't know when they will be re-added.