According to my map St Pierre is about the limit of navigation for up to 6ft draught max but as it's tidal that will probably on the top of a spring. Air draught 4mtrs as far as i can see.
I quote:
How much further (than Castillon-la-Bataille) a boat of reasonable draft can travel will depend greatly on seasonal water levels. Flaujagues (K87) is generally regarded as the limit for motor cruisers although exploration is often possible in small vessels at least to St-Pierre-d'Eyraud (K117) and in ideal conditions, as far as Bergerac (K131); hydro-electric barrages obstruct the river upstream of Argentat."
Can you access the website France Map? The satellite pics are helpful (but not conclusive).
More important, are you aware of the tidal bore and how to obtain predicted times of this mascaret which can reach heights of 1.5m?
