Francois,
Thank you for your encouraging and helpful comments. I appreciate how specific they are.
These wetlands here are unusual in many ways. There's almost no tidal effect from the moon. Instead, levels changes according to local rainfall, the volume of water flowing south from rivers originating up north, like the Mississippi, and which direction the wind blows. Because the water is so shallow, 2 to 6 feet, it's depth fluctuates quickly as the wind pushes the water into an area or out of it. I came back to this area a week later after a few rainy days and the water was up almost 2 feet.
Richard