Correct me if I'm wrong, but I think the Super Duck version is the first real amphibian in the game.
Like Skipper said, use your airbrake button to lower the Super Duck landing gear for landing on dry land. With the gear up the Super Duck will land just fine on water. Keep your speed low and your nose up though.
It is a work in progress and the Duck crew has done a great job in the short time since the release. I can't wait to see what comes next.