India, Oct. 1 -- Battle tanks were built to roll across land, not to rest on the sea floor. Yet in 1994, 100 of them took a one-way trip to the bottom of the ocean off Alabama, and fish were supposed to move in. In 1993, the military needed a way to retire obsolete battle tanks. According to the Alabama Department of Conservation and Natural Resources, the tanks went down in three rounds in 1994, with six on June 1, 58 in late July, and the last 36 on September 26.

The military realized that dropping tanks into the sea could be a good way to get rid of them. That's when the idea reached the Alabama Marine Resources Division, which started building a plan. This matters to Alabama because the sea floor off its coast is mostly flat sand. Fl...