US jets dropped four dummy bombs into fifty feet of water. The incident occurred during a joint US-Australia training exercise off the Queensland coast, during which a planned drop of bombs on to a range had to be aborted, leading the jets to conduct an "emergency jettison" of the dummy weapons.
The incident draws attention to the legal status of World Heritage Sites: what practical legal mechanisms are there in practice to protect such sites?
Designation as a WHS does not, of itself, ensure that a site is protected: that's obvious from destruction of other sites, most infamously the Bamayan Buddhas. The site of the Australian training exercise is in Shoalwater Bay, the coast of which is part of the GBR WHS. In 2005 the Australian federal government signed a long-term agreement with the US over the use of the Bay for military training. The fragility of WHSs, particularly those of nature, is starkly exposed by reckless militarism. Here's an article by the Global Policy Forum, documenting the impact of the US military invasion and occupation of Iraq.