M60 tanks undergo a thorough cleaning before use as reefs
The Artificial Reef Program used four types of obsolete Army armored vehicles as artificial reef materials off the New Jersey coast. These were cleaned at local military bases, loaded onto barges for transport, and pushed off at their final destination. Once the Army had disposed of its excess inventory, the program ceased, around 1999. The Artificial Reef Program has sunk almost 400 tanks altogether, far too many to list them here in this website.
There is a great deal of controversy over the use of subway cars as artificial reefs. There shouldn't be. Subway cars are fish condos. They are the perfect size and shape to provide homes for all sorts of fishes, as well as large attachment areas for other organisms. The fact that they come complete with large door and window openings is even better. Most reef materials, such as ships and barges, improve with age because they open up, allowing easier access to the interior. Indeed, some of the most barren reefs I have seen are those that are completely intact, since they offer little shelter.
All manner of concrete, steel, and stone rubble from dredging, demolition projects, and other construction is used as artificial reef materials. This material is generally available at very low cost or free from construction companies who are more than happy to get rid of it. Transportation costs determine where this material is used by the Reef Program.
The US Coast Guard maintains a number of aids to navigation to assist vessels entering and leaving ports, both great ports like New York and Philadelphia, and minor ports like Shark River and Montauk. At sea, these aids take the form of buoys that mark out channels and shipping lanes. The chart about also marks major ocean-side lighthouses and a few others. All of these are still extant and may be visited except Shinnecock, which was torn down.
Shipping lanes are like divided highways at sea. Inbound and outbound lanes are separated by a wide "Separation Zone, " which may or may not be depicted on the charts in this website, depending on the scale. Ships "drive on the right" just like cars in civilized countries. At the inbound end where all the lanes converge into the harbor channel, things get messy, and I didn't try to depict it. Likewise, the outer ends of the lanes are not exact either.