RE: depth charges
lots of ways to skin a cat... I would try to find some raw sodium (be sure to keep it in oil) once it hits the water...boom( this is why you keep it in oil... the moisture in the air will react with it) something the size of a 1/4 inch bb or a small marble would do it-probably be more than 'scale' size boom... Very stable until then, just don't get it wet.