Bridges today are constructed using modular sections. Sometimes these sections are rejected by DOT inspectors due to construction flaws in the concrete. This photo shows one of these rejects being put to good use in helping to build an artificial fish habitat (reef). See the next photo in this series for what this looked like after being down for a year.

Photo courtesy of the "Scuba Shack" in Pensacola. Check'em out.... they have lots of photos and info about diving and reefs! Tell'em you saw a few of them here!