I'm investigating creating a device to detect if (and ideally how many, although this seems much more difficult) there are lobsters in a trap. The trap would be between 20-100 feet of saltwater, and potentially underwater for days at a time. The design I'm envisioning would involve a water proof container with motion / proximity sensors which would communicate via a thin wire to radio beacon attached to the floating buoy on the oceans surface. The buoy would then relay the information via radio waves to shore.
I'm very new to electrical engineering so I'm not sure where to begin. I could use help understanding the more difficult parts of the design, as well as types / brands of components to purchase and test with. I'd like to build a prototype for testing on land first with a simple Arduino - after this I'll likely seek out a more minimal circuit board if possible.
Thanks very much in advance,