Hi @AdamCB -
Welcome to the forums!
Raising and lowering a camera based ond epth should work great! I’ve been chasing similar goals, but rather than a pole I plan to use a tow-fish with waterproof servos that control the angle of attach of a wing. Thus, the boat gives information on depth ahead of the vehicle, and the camera has time to ascend or descent to maintain depth. The risk of using a pole, besides having limited range and a lot more drag, is it finding out too late that it is getting shallow and an impact occuring!
A Lua script is definitely a great approach for control.
It may be possible to map aquatic vegetation at a faster rate with sonar alone - using the Omniscan SS, and perhaps software like this, which now supports it!