as long as you dont have air trapped in the pipe by capping it, pvc will sink easily, it's a good idea to have a concrete block attached to keep it from drifting. i tie a small weight to a large float, throw it over the side, leave and then come back and try to find the float through triangulation, depth finder and landmarks on the bank. even though it is visible, i try to find it other ways. if i can find the float, i know i can find the pvc when i put it down in the same place, beats putting the pvc down and then not being able to find it. i dont know why pvc does not show up, but i dont think it does, at least on my depth finders, which is one of the reasons i use it.

regards
john b.