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

Oh i remember doing that...now let me think...I don't think there's a cheat you need if I remember correctly you just need the 2 decks to be close enough for the stairs to land, you also need to make sure the decks are even once at the height you want.

I know my explanation probably is confusing but if you go to the free resort in isla paradiso is has little cabins on the water with the low deck you might be able to take a look at those and figure it out if my explanation doesn't help