i am pulling my hair out trying to find a Tether for my rov

the only option is to try and manufacturer some. i was thinking about using some cable and coating in some kind of polyethylene to make it semi float, i have been thinking along the lines of making a steel cube with a hole in the one side about 10mm. putting polyethylene in it and heating it up. putting the cable in the hole and pulling it through the polyethylene and out the hole in hope it will cover it.
the big q is do you think it will work, because if it did i could make the core up as i need it.
adam