I think, not from the surface, but have a look here [1], where the author referenced from the IIEE article has build a submergible sensor and detected (a know)

I think, not from the surface, but have a look here [1], where the author referenced from the IIEE article has build a submergible sensor and detected (a know) boat. [1] https://alexmumm.de/pgProtonMagMarine_en.htm https://alexmumm.de/pgProtonMagMarine_en.htm