Hello Dave, thanks for sharing.
I had thought of getting the device, because of the price, so interesting.
The issues I saw is that it has two sources of analog error and unquantified temperature coeffocient for each source of error.
Every “analog” device typically has a temperature dependency, This would be the depth sensor itself, which will vary the reported depth based on the varying temperature of the water. Typically small if the temperature is stable as in underground water measurement.
The second analog error – which is the current transformed to the voltage. This resistance will vary based on the air temperature. Resistor need to be selected and stated for the their temperature variation. There are resistors that have a low temperature coefficient. So the device from Seeed should state what its temperature coefficient is, but I couldn’t find it.
So just an observation, and thanks again for sharing.