How to build deck leading down to smaller deck in ocean?

I recently installed Island Paradise, and am trying to build a deck leading to a smaller deck via a small set of stairs in the ocean. I am on a lot that is partially in water, partially on land. Basically, I want to build it just like it is in the picture I provided. http://i42.photobucket.com/albums/e330/katiewashere2/20180107_002609_zpsduspsf7m.jpg
Is there some sort of cheat I'm not aware of? I built the foundations for the 2 decks, but when I try to build stairs going down to the smaller deck, the game says the stairs must be built on land. Any help would be awesome. Thanks!