Honestly, I would not put AC anywhere near a dock, GFI protected or not. In the distant past, cottages we were staying at were quite "rustic" and the GFI circuit didn't work due to a bad cottage ground. Read NONE. The water near the docks got rather stimulating thanks to someone putting a 110VAC sump pump on an extension cord into a leaky metal boat. Us kids thought there were critters in the water attacking us.
Can you get away with low-voltage lighting and products? Similar to garden lighting. Those are usually supplied by a transformer which provides electrical isolation, and the voltages are so low as to not do any harm. The GFI leading to the lighting system would be another level of protection.
Generally it is best practice to not cascade GFI circuits as it can cause false trips or the can combat each other during a tripping event and not allow one to fully trip.
Note that until I got really busy at work, I was working on a lighting solution for water areas which was a solar controller and battery setup. It has timers for dimming, Bluetooth control, water thermometer, and underwater lighting. It was quite safe since no voltage was over 12V. Maybe I should get back to work on it. Maybe when the weather goes to crap again this fall.
