The approach channel has moved to the East and the fairway mark is approx 1.6M South of the position given on ‘updated’ Navionics cartography. The co-ordinates of this mark as given in the 2020 Reeds Almanac are correct. Arcachon Marina is expensive but they do offer 2 nights for the price of 1 which, if you are staying 2 nights, makes it very reasonable. Difficult to find space to anchor outside the marina. They have an unusual system for accessing the facilities: they register your phone and you dial a number to unlock the door. Didn’t seem to work with UK phones but the French had no problems. Facilities need modernising.