It won't work
Pushing a ship either through or over the sea is vastly different to watching a drop of water dance about on a spoon heated over the gas cooker (I done that as a child, fire is great!).
If they're planning to ease the ship through the water, as ships move currently, then surely most of the resistance is due to moving the large bulk of water out of the way of the ship, and putting it back after the ship has passed. This won't change that.
If they're planning to ride the ship over the top of the water, then surely the waves will scupper that one.
Either way, sea salt will be deposited on the ship's hull, which won't help.
Even if the vapour layer does insulate well, warming the ship's hull up in the first place will require insane amounts of power.
This whole thing is just about as stupid as an article I once read in new scientist about supercavitation. The suggestion was to reduce the drag on an underwater passenger craft by going fast enough using rockets to cause deliberate cavitation at the rear of the craft. Not crashing into things like whales and other submarines would be difficult at several hundred mph, even if it did reduce drag.