Rowing boat CW key
This looks like a perfectly normal rowing boat, but is not.
There is something attached on the right oar.
Closer look reveals these two wire ends.
When the wire ends are set under water this simple circuit will notice it. BC517 darlington transistor is used as a sensitive switch.
The circuit switches power to an audio oscillator. (Little black box on the oar seen in this picture. Click to enlarge if necessary.)
No more peace and quiet on this lake. Morse code telegraphy is heard when rowing is carried out.
See & hear this video clip below. Excuse my poor CW spacing. Need more boating practise for decent fist.