I think what he (or she) is asking is what is the lowest deck that the balcony cabins facing the boardwalk start on? By looking at the deck plans
, it's Deck 9. Not sure how that compares to viewing the aqua show, as I haven't been on that ship.
On the hyperlink, it defaults to deck 3, but on the left side of the page, you can choose what deck you want to view from the drop down menu.