From the top of the Chassiron lighthouse, at the end of the Ile d'Oléron, you can enjoy a panoramic view of the Atlantic Ocean ... and at low tide you can also see fish locks. Explanation.
It is a fishing technique used since the Middle Ages. Low walls of stones and corals are arranged, we see them here, it is these lines and these curves and in these basins the fish that come to get lost during high tide remain trapped there at low tide. The water is then emptied through locks that the fishermen open.
In WS, see a fish lock but on the ground.

A traditionnal fish lock but here on the ground, interesting to well understand the use of these locks for fishing.