Some pictures of the French-Spanish border at
http://www.bidasoa-txingudi.com/ing/pres/pe1.htm
The last picture, although it doesn't say it, is the Ile de la Conférence.
The first picture is the Bidasoa estuary (one 's' in Basque, two 's'es in French and Spanish) and
the bay called Txingudi in Basque (In French: Baie du Figuier. What's it in Spanish, I don't know).
This bay is subject to a special border agreement: much of the water surface is a Franco-Spanish
condominium, just like the Ile de la Conférence. The bay stretches between the cape called Higuer
(Figuier in French) and the Pointe de Sainte Anne. A little map can be found here:
http://www.shom.fr/pro/cc/html/cartes/carte6556.htm . Disregard the boundary on that map: it is the
municipal boundary between Hendaye/Hendaia and Urrugne/Urruña.
Peter S.