Make passageways or even deactivate mines using signal from the same cable it is safeguarding. Ship needs to pass, captain sends an SMS from a sat and the mine is deactivated for half an hour. If ship is suspicious, a destroyer escorts at at gunpoint - cable signal lost, torpedo goes off automatically.
Great idea. I was thinking of something similar after 9/11. Install explosives on all commercial airliners and have them automatically detonate and destroy the plane if it gets too close to a building where it isn't supposed to be. It's foolproof!
