Elo River in Magelang is nice place to start having fun. This river is suitable enough for beginner. The stream is medium, even in rainy season. I've ever been there once with my friends. It was rain, and seem frightening seeing the river stream. The instructor was giving me buoy and paddle and we (I, my friends, and one instructor) start our journey. All electronic device, like phone etc, was put inside a water resist box, so it save during rafting.
The stone, water, stream, which were look frightening from riverside, became interesting part while rafting. Bigger stone, bigger stream, more interesting. I wonder if the stream was bigger after the end of rafting. At the end, you probably lost your voice for a while because you're too much screaming all the way.
Ok, i'm not good storyteller btw. But what i wanna tell you is simple. Get your ass to this place and get some fun.