African Area Boat Question?

Question

My 9th grade History Teacher asked our class what the "High Frequency noise producing" device used on ships in and around Africa to ward off thieves during transit (Pirates)?

Answer 1

http://gcaptain.com/maritime/blog/future...

Its not operational yet to the public. Its still being developed by the military but it looks like it will work for maritime security.

Answer 2

to keep away from the edge

Answer 3

Maybe the Dragon Boat, The African Queen or the Jungle Cuise. Maybe it's one of them. ( Not sure )