I have never surfed, but IT IS the original sport from which all other board sports evolved, so probably the most free feeling of all.
However, I do longboard and it does feel a lot like snowboarding(if you have the right board). Carving on my Loaded Dervish(flexy board made for carving)feels remarkably like carving on my SL. Furthermore, doing speed checks and stand up slides feel like slashing and heel side stops on a snowboard.
The learning curve is pretty fast cause you already have the board skills. All you have to do is learn to push and foot brake correctly and you'll be getting your stoke on daily