I’m sure you will figure this out. Sometimes we have to take a step back to move forwards, if that makes any sense…………………. and they say that everything happens for a reason.
Can you use the brown as a base for another top coat of a different color ??? Just letting enough of the brown to show through ??? It might make for a smoother transition to the blues and greens between the water and the shore.
From what I have seen from visiting various lakes and rivers, the green (and brownish green) colored water is normally more shallow, and the darker blues are more deep. Just like you have posted in one of your pictures above.
However the aquamarine and turquoise colors are more of a “tropics” or beach shore line type setting. Something like you would expect to see on a Pacific Island (or something from the Caribbean).
I have been thoroughly enjoying watching the progression on this build, and will be looking forward to your next installment.