Water Depth Under Bridges

[tclC-18]

I am sailing a Catalina 18 in the relatively shallow waters of the Caloosahatchee River around Ft. Myers, Florida. There are a number of bridges in the area, and the NOAA charts seem to show that, generally, where these bridges are located, there is adequate water depth for my boat (which draws only about 2.5 feet). I am confident that I have ample water depth in the main channel under the central span of these bridges.

My question is this. Because the NOAA charts do not indicate any special water depth limits or obstructions under any portions of the bridges, can I assume that the water under the other spans of the bridges is what the NOAA chart is otherwise showing for that part of the river? Or do I need to be extra careful about using anything other than the main channel under a bridge, even though the chart does not show any special depth limitations under other parts of the bridge?

Thanks.