I have done (and documented) installations that deviated from 7671, no big deal, you just have to be very sure that you have thought it thru, and labelled anything that deviates from what some future sparky is expecting.
If you are not prepared to stand behind your work in a court (Or, shudder, in front of a coroner), should you be doing it?
Time was that it did not list marine locations as 'special', and you want nothing to do with TN-C-S in a marina, so we used isolating transformers to separately derive power for each outlet (With RCDs on the secondary side, post secondary earth bond connection), way outside the scope of the standard, but it worked well and we had no problems with it.
Regards, Dan.