I remember sailing on Radiance of the Seas years ago and passing under the Lions Gate bridge as we entered Vancouver Harbor. The ship could only clear the bottom of the bridge by about 3 meters, and only during low tide. It was pretty “interesting.”
I spent a week this summer on the Kennebec River in Maine, about six miles below the Bath Iron Works at Bath, Maine where they build a lot of Destroyers.
When I studied the charts I was amazed to see the channel was only 30 foot deep in spots. The ships go out at high tide when another six foot of water is on that, but none the less I didn’t believe that none of the hundreds of ships built at Bath for the last 110 years draft more than 30 foot.