ok, so if you're problem is staying up, then here's what you need to do.....
knees bent, feet shoulder width apart, back straight (this is the most important), don't hold the rope in close to your body like you would a baseball bat - keep it out in front of you to the point where you have a slight bend in your elbows. for reference, my elbows are at about 130 degrees most of the time when I'm skiing. this is a key point of control.....a lot of people break at the waist and this is where they go wrong and start wobbling all over the place and then crash...DO NOT break at the waist...keep that back straight!!!
you do these things and I guarantee you that you'll be skiing along. source - me. i've been water skiing competitively for over 20+ years.