The old method I used for it involved a repeated schedule every 20-30ms and an invisible player model to your side which "you" controlled and could look from. While this method worked, it lagged the game horribly whenever more than two or three people used it at once and occasionally crashed servers if you went in water.
I did attempt to remake this by using the player type attributes for the camera, to see if it was possible - while I could place the camera to your side (as in the Survivor player, but more so), I could not rotate it to face you as such an option doesn't exist, which makes the player type useless. (You wouldn't actually be able to see yourself in third person...)
I haven't found a better method to do it with so I'm currently not trying to.
