Up to 1940 mines were moored in deep water and swept with cable and paravane.
Ukuya kwiwaka elinamakhulu alithoba namashumi amane ezigcayiseli aqhina izikhephe ngentambo emanzini anzulu ze asusa ngentambo enkulu yocingo nesixhobo sokuhlasela phantsi kwamanzi zisike ezo zigcayiseli zibotshelelweyo .