The foil is an interesting idea. Now that you mention that, I can’t believe the cable isn’t shielded to start with like coax or the VHF antenna wire. ?? There is the outer black jacket and two inner conductors with their own jacket.
It seems like their should be some easy rules that marine electronic makers give out (but that would be too easy). Some I have wondered about are ground batteries to aluminum boat to have common ground with water? This would allow a very unified ground vs. the relative grounds that exist when you start moving lots of current around (like with trolling motors) with dedicated return ground wires.
P.S. It is the transducer that I waited a month to get.