Boucau is the most Northerly village on the Cote Basque (Pyrenees Atlantiques Departement (64)), by definition of the realms and boundaries, with the Landes Departement. Yet by another definition, because it is located above the river Adour and sighted with Tarnos, it is the most Southerly Village on the Cote d'Argent, although not actually on the coast, but just 1 km (just over ½ a mile) from the beaches
The reasons for this confusion as I have discovered (but not had confirmed by authority), is that some time back in the distant past, Bayonne in the Pays Basque & the Pyrenees Atlantiques Department (created from 3 of the original 7 provinces of the Pays Basque) wanted total control of both Banks of the River Adour Estuary & Port, and so the decision was taken to include Boucau in the 64 Department, but as I understand it, Boucau was never originally in the Pays Basque (a separate Country up until the late 16th Century). (Still confused, so am I).
Tarnos & Boucau are located in the heart of a vast tourist region and are exactly half way between the Landes coastal resorts & pine forests, the Cote Basque and Pyrenees Mountains.