The open question is still a building built out on the end of a pier. There is nothing I see that prevents you from having the service equipment on the pier but it looks like you still need the ground electrode back on the shore. For that matter even if this is a 250.32 building, fed from a service on the shore, the required ground electrode at the building will be back on shore or a made electrode on the bottom.
"I ain't inspecting that one in the winter"
