Dravon,
realistically it is way outwith any home made way of doing such a thing easily.
The best you could manage would be to use a transmitting transducer on the ROV and receiving transducer on the surface. Send a pulse down the umbilical to the ROV, transmit it through the transmitting transducer through the water and measure the time between transmitting the pulse and receiving it on the surface. By using an average speed of sound in water of approximately 1480 metres a second in water, you can calculate the distance from where you are on the surface and the ROV. By knowing the depth of water the ROV is working you can then calculate the horizontal distance the ROV is away from you.
Good luck with that 😀