Make depth charts
There are several ways to collect depth data through various wifi devices like Deeper, sonar phone, Raymarine and more.
My idea is to collect the depth data from these sources and combine them with position data and make a small version sea chart for small lakes.
In some cases there might be position data included together with depth data in NMEA protocol.
Use these data to make a depthchart over your lake.
A manual way there I crunch the depth to gps position on a slow drift over a area would be nice to.