Probably the best idea would be to go swimming in the ocean with whomever you'd like to contact, since salt water and mechanical agitation probably diminish the

Probably the best idea would be to go swimming in the ocean with whomever you'd like to contact, since salt water and mechanical agitation probably diminish the reliability and functionality of most listening devices. But there's a continuum of practicality here. It's hard to imagine the Soviet commissars hopping in the water for an afternoon meeting.