I think that SH3 engine might not be able to do that, but someone like Seeadler could probably give a better answer. Right now, you can represent with different colours the depths and heigths, but not MARK with lines the contours. In SH4, though, shore lines were marked and I know Seeadler eliminated them. So it might actually be possible to outline the different depth areas in SH4, but I can't tell for sure
Would be a mod I myself want to see