Two Marine jets dropped four 500lb bombs on the Great Barrier Reef this week after a fuel emergency meant they could not land while carrying the weapons.
The AV-8B Harriers, part of the 31st Marine Expeditionary Unit, had been taking part in a training exercise when the pilots realized they were running low on fuel.
Each Harrier was forced to drop two bombs on the UNESCO world heritage site, although there was no risk of them exploding, according to defense officials.
The bombs were dropped about 16 nautical miles south of Bell Cay in the Great Barrier Reef Marine Park, according to NBC News.
Defense officials said they tried to pick a location that would reduce the risk of damage to the reef, and said the bomb site was in a ‘deep channel’ about 60 metres deep.
The pilots were supposed to drop the bombs on Townshend Island as part of a training exercise, but at the last moment they were told the range was not clear.
At that point, they realized they did not have enough fuel to return to the aircraft carrier USS Bonhomme Richard.
‘Due to low fuel and inability to land with the amount of ordnance they were carrying, the on scene commander determined it was necessary to designate an emergency jettison area for the ordnance,’ U.S. Navy Commander William Marks told News AU.
‘They chose to save the aircraft,’ a U.S. official said. Harriers are said to be worth about $35 million.
A spokesman for the Australian Defence Force said the bombs were a ‘minimal risk or threat to the public, the marine environment or civilian shipping transiting the reef area’, and added that Australia was investigating the incident with the U.S.
The U.S. Navy has already started a salvage operation and the Marines are investigating the incident, but added that it was unlikely that the BDU 45s and GBU 12s would explode.
BDU 45s are training bombs that mimic several types of bombs used by the armed forces, and the GBU 12 is a laser-guided weapon.
It is not yet clear what the impact will be on the Great Barrier Reef. Its world heritage status means it is strictly governed by a series of rules that limit development and activities in and around it.
The world’s largest coral reef, covering more than 1,200 miles along the coast of Queensland, is a fragile eco system filled with marine life, from endangered green sea turtles to dugongs, or sea cows.