Whether you'd like to pay your respects or understand more about the history of the building, Eglise Saint Eloi is an interesting site to visit. Check to see if this sanctuary is open to tourists to experience the peace and quiet inside.
You'll be spoiled for sightseeing choice when staying in Andernos-les-Bains. Eglise Saint Eloi is a good place to begin here, but there are lots of other worthwhile sights to check out. Port d'Arcachon, Taussat-les-Bains Beach, and Ares Beach are close to the house of prayer and and will cap off your day nicely.