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

Ok, I did it exactly as it says in the tutorial, and I was able to built exactly 4 steps, but when I tried to a 2nd set leading off from the base of the first set, it says "Can't place underwater" even though the placement of the stairs is 8 squares away from the water, or it says "Can't level terrain". I also tried it with the constrainfloorelevation false cheat and still nothing.