Originating from the age-old belief that water springing from the depths was endowed with healing properties, spas, which first blossomed in the West during the heyday of the Roman Empire, again gained importance and fame in the 18th and 19th centuries, as the increasing medicalisation of thermal water drew crowds to the best-sited or best-organised watering places of European economically developed countries. As, in most cases, none but the social elites could afford to spend time and money in such spots, investment followed, both in terms of architecture and of leisure, since visitors, after having been convinced by their physicians, high society journals or word of mouth, had to be kept happy as well as made fit. Simultaneously competition grew as spas vied for patronage, both within national borders and across Europe, the alleged quality of their waters being flaunted in the jingoistic battles of words which served as forerunners to the grislier actions of WW1. Being the major lieus of high society leisure and pleasure, spas underwent the same decline as the prewar moneyed classes which patronized them and lost ground, both to more exotic destinations and to seaside resorts, which, likewise, promoted health and well-being, but in a less elitist environment and at a cheaper price. Thalassotherapy, grafting on the success of the latter and making much of the relaxation and physical fitness derived from natural elements such as seawater or seaweeds, is the latest avatar of that long story which the papers of the conference held in Brest (France) in May 2005 here purport to tell.