I'm supposed to "create a swinging motion" with the two hanging balls of rock, to release the larger one and thereby plug the stream. Not getting the hang of it after LOTS of trying. I've been able to nudge the large rock, but nothing that would suggest I'm getting close to dislodging it.

Is the idea that the two rocks swing in unison -- or alternately?

Is there a better way to get them rocking than shooting with the Uza-shi?

(And yes, I tried to just blow them up with dynamite. LOL)

The idea is supposed to be that the smaller rocks swing with unison and with enough force (larger amplitude of swing) that they dislodge the large one. It took me about 5 mins of trying, but I succeeded even through the smaller rocks weren't 10'% synchronised. First get one rock to full swing, then adjust the second one using weak rapid fire from the 1st weapon to sychronise it with the already swinging one. It doesn't have to be perfect, the game engine is quite forgiving. Still, it's tough, but the "swinging box" quest in Talanzaar prepared me for this one. Don't forget to move out of the way through the small door you came in as soon as the large rock starts to roll!