Are the buoyant? I'm thinking you need a buoy or something to keep it off the bottom? Otherwise they will sink into the silt, right?
According to the plans that came with the ones I bought, you make one piece of pipe 6 - 12 in longer that the others.
Drill a couple screws into the bottom of that pipe perpendicular to the pipe.
Get some small cheap plastic buckets about 4 - 6 inches deep.
Fill the bucket with cement and push the long pipe into the cement.
Bury the buckets with concrete into the bottom of the lake to anchor the porcupine.