How do I get off the dock if I am on a line pulley system and I start sitting?

You should start sitting in the water so that you are floating on your back with your board in front of you. Make sure you can see ahead of you and that the cable is on top of your board, not underneath it. When the cable is about to start pulling, bring your leading foot out of the water more, so as the cable tightens you are pulled out of the water until you are squatting over your board with your leading foot facing the cable course. Once you have gained a steady speed and balance, stand in the upright position with your knees bent and your center of balance over the center of the board.