The Réseau des Bains de Mer (RBM) was a group of five metre gauge railways centred on Noyelles-sur-Mer, with a total route length of some 68 kilometres (42 mi). It was a part of the Chemins de fer départementaux de la Somme. Three of the lines are still open as the Chemin de Fer de la Baie de Somme heritage line, and are dealt with under that article. This article covers the other two lines, now closed. All the lines were in the Somme department. The five lines were:-