Put the tether in "figure8" in plastic box to aviod twisting.ROV can pull out, but You have to manually pull in again.100 meters in box, box appx 60x30 centimeters
When handling cables on ship we'll figure 8 it on deck. Lots easier and faster than having to "tuck" a turn when coiling. But figure 8's take up more space. I've thought of mounting a couple large diameter pipes to the bottom of the crate to keep the coils neater.
Some large PVC pipe would make for a neat coiling post. Mount solid to bottom of box.