Water in the water bowl? Or use some other medium like sand or clay bricks etc?
I suppose You are speacking of WSM (I don't know wich model). IMO, you should remove water pan and put inside a foiled pizza stone .if you like some water put it in the drip pan just over the pizza stone or in a pot over the meat grate.
Pizza stone will help you with its termal mass to steady cooking T.
My 22 WSM cooks always @250F super steady.
another vote for no water. just foil the pan. my first cook i used water, and the clean-up was a huge mess. never again.