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.
I find this sort of material to be much more interesting than the endless rehashing of coral reefs, glowingly useless gear reviews, and "buoyancy tips" that fill up the standard glossy diving magazines.