I'm pretty sure that's due to saltwater's conductivity, not any EMF considerations. Conductivity will result in some partial cancellation of the AC magnetic fie

I'm pretty sure that's due to saltwater's conductivity, not any EMF considerations. Conductivity will result in some partial cancellation of the AC magnetic field. But not enough to matter at 60 Hz, which is within the Extremely Low Frequency band used for communications with submarines. https://en.wikipedia.org/wiki/Communication_with_submarines https://en.wikipedia.org/wiki/Communication_with_submarines