I'm not sure if this is a design trick nobody but me has used before, seeing as the trick is actually very simple. But I don't recall ever seeing it outside my own scenarios.
Using ice and the contrast between deep and shallow water, you can create realistic icebergs and make wintery seas a little more interesting. Or make a Titanic scenario, should you wish.
I discovered this trick while designing "A Christmas Story - Director's Cut", back in 2006, and used it again in my PTC entry of 2008, "Footprints in the Snow". As far as I know, it hasn't been used anywhere else. I could be wrong of course, so tell me if you find an earlier example.