Hi Stoker,
41 foot tide is something to be reckoned with no doubt. Your water taxi ride made me try to look back at what it must have been like a century or two before ...... but I didn't have much luck conjuring a proper image.
Yesterday or was it the day before when I was young Cardiff was still a coal port with nearly 7 miles of wharf. Several dredgers continually dredged the bay and my great uncle was a dock pilot. Because of the high tides as many ships as possible had to clear the sea locks day and night as the tides allowed. The ships nearly filled the locks and it was a very skilled job getting the ships in and out, two pilots were needed one in the wheel house the other walking along on the dock side. And before the advent of radio all the communication was done using whistles. The pilot in the wheel house not being able to see anything relied totally on his mate.
I had a quick search and found the following which gives an idea of what it was like; apparently in the early 1900's it was not unusual to have up to 100 colliers awaiting docking in Cardiff Roads. Coal as certainly King!
https://www.flickr.com/photos/ben_salter/sets/72157600049669187/Take care.
Tony.