I got halfway through #10, so created a water gun that shoots no damage. Started working on making the water drops explode when shot with the other gun, but ran into a bug where the water exploded instantly as it was shot out. So I just ran around with a self AOE explosion. Maybe good idea for something else but not this one.
I will keep trying to fix that bug tomorrow, hopefully finish #10 and move to #11 if I feel up to it.