The sea lamprey is a parasitic eel-like fish found on the Atlantic coasts of Europe and North America, in the western Mediterranean Sea, in the Great Lakes and even in the Thames. It has a suction-cup like mouth full of sharp teeth, and it doesn’t take prisoners, but let’s them bleed to death or die from infection. It usually doesn’t attack humans, but oh well it has happened even to open water swimmers.
Anyways, Michigan State University has developed an effective lamprey repellent, that gets tested in the video below.
Aand there is an underwater view as well. Really nice, via Geekosystem.