The Iranian "Flying Boat" is actually a "Wing in Ground Effect Vehicle". The vehicle can fly at low altitude only. It is not a flying boat in the usual sense. I bet our naval analysts are laughing at this one! The reason they don't say anything is that this Iranian device could be used as a pretext to clobber them when the time comes. If they are trying to scare the US with this, they have badly miscalculated.
So, it is like the old Russky ekranoplans. Also this thing is said to travel at 100kts - sheesh, you could engage the d@mned thing visually. It does look like a nice gunnery target.
Here's another page with all kinds of historic pictures and movies of these WIG boats. http://www.se-technology.com/wig/index.php