DRD II,
If you are looking to create fish structure maybe you would be better served if you would put your structure on the bottom in the form of hardwood pallets and such. It sounds like you are in some shallow water yet. Make sure that you take and tie bricks to the structure as to keep them where you intended them to be. I am not sure what depth that you have or what kind of slope that you have but 8-10 feet are great area to consider for pallets. Hope this helps.