I live on a natural lake that is going thru a dredging process.  The lake has hydrilla, eelgrass, lilypads everywhere, but most my fish are coming off these pipes that are above and submerged on the lake.  

I'm amazed with all the vegetation that they are hanging around these pipes.  

The pipes are unique.  And I'm sure the structure provides shade and other attributes.  It is also now over deeper water and next to a "drop off" that it made.  All good things for hungry fish.  Often times something that is "different" will be the key.  

Also, just because you are catching them there doesn't mean that many of the fish aren't still using the various grasses.

Also if water drains out of those pipes in the water. It will be a more oxygenated area than the other water.

Good points guys.  I just recently found a drainage pipe going across a cove at Lake Accotink in Springfield, Va and I ran a Mann's Shallow Running crankbait along it.  First cast, BAM fish on.  Looks like drainage pipes can hold fish.  There is a dredge project going on in that lake and it has been since the late spring.  Normally I spend most of my time fishing laydowns at Accotink but now I have this new area to work.  This cove is in the back of the lake and the only people that ever see any of it are normally the bikers because the trees block the view.

this is what the structure looks like where i live.