I have just returned from that area, though I wasn't visiting by boat.
It is worth a visit. St Valery has a small marina and the town is very pleasant. Good food - particularly the sea food.
Miles of sandy beaches.
Whilst there I saw a fin keel yacht high and dry on the bank. The area is very tidal and vast areas of sand appear at low water. People walk out at low water but the coast guard is watchful becuase of the tides. From the shore the main chanel appears well marked and the main headlands and harbour entrances are well lit.
If you can take the ground you could have a sand bank to yourself. I saw quite a few small private fising boats doing this.