So there are very mixed results

genec has a great pic of PVC with hardly any algae from his DI

Others can hardly spot PVC until it is all covered with algae

Others have cover out that is invisible and if they don't get coords when they drop, they might as well forget it!

That's why I wanted to see if PVC would act the same as a ping pong ball or a fish bladder. Seal one shut with air in it and see if it will show. I think it would still be nearly invisible to fishermen who didn't know where to look....they would only see a single bright spot. But the guy who planted it would know where to look and what to look for. I was hoping if I put out an 18-24" piece, horizontally, it would show up as the brightest stick in the world! Drop a buoy!!