I looked at the article on Water Hazard and it shows "intermediate" in the Flash version and "advanced" in the Mobile version. To me, and that is just my opinion, I think this track is a lot harder than I credit for "intermediate", as there are not good places for Spike Factories, Banana Farms or other large-footprint towers, and also because of how much a pain it is to me to split towers into two separate less-powerful groups instead of one single tower of more upgrades for the same thing.
In your opinion, what do you think the difficulty should be?