Containers at sea–Part II
The Container Owners Association calculates that a fully loaded 20-foot dry freight container will float because its volume displaces 83,000 pounds of water, more than its weight of 30 tonnes or 66,000 pounds. Mathematically, it would float with 18 inches sticking out of the water. However, if water enters and increases the weight to over 83,000 pounds, the container will sink. Floating containers were previously shot at or exploded to sink them and reduce their danger to ships because this was less expensive than salvage costs for towing and recovery. This is now illegal because of the pollution risk it poses.