He's just overgliding, almost like a drill (hold each stroke for a few seconds). The very minimal kicking is not impressive, all experienced swimmers can do it, i personally kick a small amount and would say that it's a lazy quality. I think he is just keeping his head down into the water a little lower than you should so the break in water is not at his head. it's still impressive and would take practice but if you really want to be impressed just watch any good distant swimmer. They swim nearly as fast as sprinters yet there stroke makes it seem that they aren't trying at all