A pair of reports put out by the Navy today outline how the Navy is going to “inadvertently kill hundreds of whales and dolphins and injure thousands over the next five years,” says the Associated Press, “mostly as a result of detonating explosives underwater.”

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On top of the underwater bombings, the Navy says that its “testing and training” exercises are also probably going to temporarily deafen millions of marine critters. The detrimental effects of sonar on whales and dolphins has been a controversial topic for the past decade or so, since at least 2001 when another Navy report found that sonar had contributed to the deaths of “at least six whales.”

The Navy does the bulk of its training in four places: off the East Coast, the Gulf of Mexico, and off Southern California and Hawaii, and it would like to continue doing so. But, in order to get the permit it needs to do field training for the next five years, the Navy has to study how its activities could affect marine life. That’s where these new environmental impact assessments came from.

For their part, an official blog post from the Navy says that they are very sorry not sorry for the forthcoming deaths and deafenings:

Active sonar operation and underwater explosive ordnance handling are perishable skills that require training at sea under realistic conditions that cannot be replicated by simulation alone. Newly developed systems and ordnance also must be tested in the same conditions under which they will be operated. Without this realistic training and testing, our Sailors cannot develop and maintain the critical skills they need or ensure that new technology can be operated effectively. We have proactively coordinated with regulatory agencies and adopted their suggestions for standard operating procedures to protect marine species and the environment wherever possible, such as using trained lookouts to avoid marine mammals while underway and ramping down or halting sonar if marine mammals approach our ships within certain safety zones. With the care and diligence of Sailors like you, we have been able to protect marine life without jeopardizing our ability to conduct essential training and testing.

More from Smithsonian.com:

Navy’s Plan To Go Green Is Falling Apart

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The Navy’s Future Is Filled With Laser Guns