a 1964 US Air Force instructional video on how to defend yourself against sharks. Rather amusing.
To kill a whale
During the 1980s, a technique was being developed by the US navy to detect submarines - a sonar, which unlike regular sonars (which rely on sound created by other vessels) worked through emitting a high power, low frequency sound and then listening for returning echoes. The noise emitted was around 230 decibels, which is around 10,000 times louder than a passenger aeroplane taking off.
As you might imagine, this had some severe effects on marine life:
It was shown that some animals further away from the source were deaf (which is a drawback for animals which rely on being able to hear for reproduction and even feeding sometimes). Closer to the source, 13 Cuvier’s Beaked Whales were found washed up on shore with severe gas embolisms and haemorraging as a result of the pressure waves created by the sound.
180 decibels causes permanent death of hearing tissues in humans, why should the marine environment (which is even more sensitive to loud noises, due to the nature of water) be exposed to it? surely any technique which made use of such loud noises would be banned on land.
Above: How active sonar works, gas embolism in a dolphin liver and a Cuvier’s Beaked Whale.
