He added the ultrasonic speakers are lowered into the seabed "a bit like a lobster pot".
To discover more fascinating science content, head to bbc.co.uk, search for BBC Inside Science and follow the links to The Open University.
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當局表示，被攔截的無人機碎片掉落在著名的帆船酒店（Burj Al Arab）外牆，造成「小型火災」。
На шее Трампа заметили странное пятно во время выступления в Белом доме23:05