The 1 K ohm resistor is lead weight suspended just above the underwater bottom.
Tied to boat cleat on back of boat above is specially made switch with free swinging arm ( in simulator, shown in neutral position. If boat drifts the lead weight drags on bottom and will swing the arm and make contact which sounds the alarm. If weight rests on bottom and weight line goes slack a spring will lift weight suspension bar and contact another alarm switch that the depth clearance has lowered and crew needs to give attention to boat.
Also, this circuit is handy for feeling your way into strange harbor or in fog to reach anchorage.
