Mate, I've spent m life in shallow waters, mostly in aluminium tinnies. Started years ago without sounders or GPS, 40 years ago, and still nowadays but with the 'benefit' of sounders and GPS... simple rule, go SLOW. Sneak into the waters with GOOD SUNGLASSES (UV glare, so need polarised lens) on so you can 'see' trouble. If water is murky and not see clearly, I lift my motor up into the highest position and motor slowly into the areas...
With sounders, you get the readings and can then take note of when your front hull bottoms out (noting depth for future reference), and can then easily back out before running aground... now with GPS, you have your track line so know where you back out and so where it's 'too shallow'...
In my current boat, I have a Garmin EchoMAP sounder / GPS which as the 'quick contours'.I have it running all the time... this feature actually makes it own maps into your chart, with contour lines etc, so you have BOTH the updated detailed map when you go back AND your track lines.
I believe the Lowrance units have a similar 'mapping feature' but not sure which models etc.
Regardless of tech, going SLOW and creeping in is THE solution. If you also flick lures, you can fish your way in so as to not disturb the flathead lying up on the flats.
Using an electric motor would work too, but I don't have one, use one. I just motor up slowly. Sometimes fishing on way in / up, other times, just slow pace in.