At the bottom of the oceans and seas lie more than 8,500 shipwrecks from two world wars. These wrecks have been estimated to contain as much as 6 billion gallons of oil, as well as munitions, toxic heavy metals and even chemical weapons.
For decades, these wrecks have largely lain out of site and out of mind. But all this time, their structures have been degrading, inexorably increasing the chances of sudden releases of toxic substances into the marine environment.
