Trevor and I want to do some depth mapping of the bay in our boat. We looked at using underwater sonar transducers like those from MaxBotix but they’re usually water-resistant and not waterproof. (I guess that one’s IP67 rated – someone in a forum said they’ve still had issues.) So now we’re looking at fishfinders and pre-built depth gauges. To get the data out we could open them up, listen in on the RF comms or maybe just take periodic images of the screen.