Mbele TV

I shot my videos using a T3i and I'm editing my clips using Magic Bullet Looks. I have a waterfall cip and I would like to reverse the flow of water so that it appears to be flowing backwards, then foward in a type of loop. Its a moving shoot (camera tilts downwards) so I'm thinking that I need to isolate the water in order for this effect to happen? Can anyone advise me on how to go about doing this?