Desperate for advice and help!!

Hi there guys having a little trouble!! I ride both the cable and behind my friends Malibu VLX, i have only been riding the cable for about 3 months and have reciently learned Ralys, Backrolls, Kripts, 911 and my belair all to a very good standard (If i must say so myself!!) My problem is my true passion is behind the boat and i am having a really frustrating time learning only my first Invert (Backroll). Does anyone know if a Raly behind a boat is, in anyway simular to the cable??? If i could do ONE cool thing behind the boat i think it would fuel my motivation!! Oh yea i have been riding behind the boat for just over a year, which again is kinda winding me up as i want to be much further than i am!!!