You could use the Tinsley 5930 for cable detection, it’s currently diver held but modifications could be made for an ROV version. The tone carrying frequency is anything from 1-100Hz and is usually switched from the Power Feed Equipment at the shore end, failing that an off the shelf tone generator can be used.
Have a look at http://www.insight-marine.co.uk/tinsley/ for a bit more info, may be a good alternative to TSS/Innovatum considering all the issues.
Cheers
Alex
