i dont know much about them but couldnt you just buy some bouys, rope and some concrete. pour the concrete into a bucket and put a loop of rope through it, so it makes a handle thingy formed in the concrete. and then go and put the concrete anchors down and cut the rope to the right length and tie the bouy to the top?
im just guessing tho
x x
o
x x
o
x x
o
x x
o
x x
and set up the buoys like so, x and o are diff colors, and the boat drives through the x's, skier goes around the o's