In the middle of the rope I tie a loop through which I pass the end of the water line. Once the loop is tightened around the pipe I double tie another not around it. This helps ensure that while the water line is anchored in place by the cement block, the float helps suspend the water line off of the bottom of the lake preventing any sand or debris from being siphoned into it. Submerging the water line. Now comes the fun part, getting wet.
Some people like to where hip waders when they walk the water line out into the lake.
With the end of the water line in tow, I simply walk backwards into the lake being careful not to crease or fold the pipe in any way. Once I've gone as far as I can go and the water line is taught I drop the anchor on the lake bottom and make sure there is enough slack in the rope attaching it to the float that a large wave won't lift it from the bottom. While I'm out in the water, I usually try and fill that part of the pipe which stays in the lake with water. This makes for less work later-on while priming the pump. Essentially, the more water that you can get into the water line now means the less water that the pump has to suck up later.