Well, I can tell you that the first picture of wakeskating in wakeboarding magazine appeared in the april 1995 issue. I'll try to attach a pic of it at the end of this post and hopefully it will work. I don't have an idea as to when it was actually "invented" but people started taking it more serious (from a financial standpoint) in the late 90's, say 1998ish with Fresh water traction.
Wakesurfing has been around since wakeboarding magazine was first introduced because if you look back, there are ads for wakesurfers. Like wakeskating, it wasn't taken seriously until people saw the opportunity for $$$$$$$$$$$$$$$$$$$$. I have this wakeboarding magazine from august 1995 that has byerly wakesurfing in the back.
Is there any specific information you would need for this project? I have every issue of wakeboarding magazine (minus april 1994) and I could provide you with a few pics (the wakeskating one, the byerly wakesurfing one, etc) or interviews if you knew what you were looking for. Well, if you have any specific ideas for information just post it. Good luck