that is exactly what you need to do, just lean back and put pressure on your back foot. The thing is that you have to stay like that until you take air. In the air you do your tricks and then to land you have to again put all your weight in the back, so you the rope does not pull you forward when the impact happens.
It's kind of complicated because for the snowboard you only have to worry about the lower have of the body, here its a mixture of upper and lower half. You really need to keep control on your upper half to maintain stable in the water.