I have troubles with definition of the communication technique to use in my project.
I would just like to let communicate two arduino, one at sea level one at ground level with sea water as medium, as described in the attached scheme.
I am just trying to understand wich kind of technique I can use.
I made a link budget with RF Tx/Rx but it seems to be not applicable.
What about Ultrasound/Acoustic? Which one is the easier/cheaper to implement?
Consider that the only data that I have to transmit to the Arduino at the bottom, is just a 1/0 bit (ON/OFF) and no more.
Thank you in advance for your time!