I'm sure my other settings had something to do with it but the land percentage should trump the other randomness.  In my case I have a massive pangea with land covering the entire map despite my map settings.

I had the same problem one time. I guess the problem is that the world shape (random in your case) does contain no ocean. If this one is selected it seems like the map generator is ignoring the land mass value (which makes sense in my humble opinion).