Only the U.S. Navy can spend $20
million to sink one of its own ships:

The Navy spent more than three years
and $20 million preparing [the aircraft carrier] Oriskany
to become an artificial reef. The project was repeatedly
delayed to meet Environmental Protection Agency concerns
about removal of hazardous substances including oil, fuel,
asbestos and PCBs — polychlorinated biphenyls, which are
cancer-causing substances used throughout old ships in
electrical equipment. Even then, for a while, it seemed as
if the 56-year-old flattop might never go down. She was
towed between Pensacola and Texas three times before the
sinking was set.