If I have a PPL-ASEL, what would I need to fly an LSA-ASES?

I'm flipping through the FAR/AIM 2010 right now, but maybe someone else might post the answer before I find it. There was this light sport seaplane in the movie "Knight and Day" which I am very interested in. First, does anyone who's seen the movie know what kind of plane it is? It's a high-wing single engine LSA that sort of uses its fuselage as a hull. Second, what would I need to fly one if I already have a private pilot's license for single-engine land? Is it just an endorsement, or would I need a new rating, even though the sport license would technically be superseded by my PPL?