@jonathan - Interesting friends you have

I'm not pointing to anything professional as Aurora but just as a hobby to take videos of the deep sea - fish and other things.
@Shanook - Maybe I will start by something dragged by the boat but I doubt that this is any practical in such depths. An ROV is my final target.
I have 2 main problems -
first the trust motors since for such depths these have to be magnetically coupled - if someone has more details about these pls let me know.
second the transmission cable - I am thinking about fibreoptic so as to minimize the drag and cable weight but this is all new to me so if anyone has more ideas I be happy to know.