La Source Bleue

Character of La Source Bleue

La Source Bleue, also known as La Papeterie, is located near Villiers-sur-Marne in Haute-Marne. The spring emerges into a striking blue-green pool on the grounds of Hôtel La Source Bleue. Behind its idyllic appearance lies a technical cave-diving system that has been explored since the 1960s.

The first passages begin with a funnel descending to about −5 m and two restrictions. At roughly 15 m from the pool, a larger underwater passage is reached at around −11 m, approximately 4 m wide and 3 m high. It then descends to about −15 m. At around 62 m there is a chamber, followed by a narrow fissure historically known as Le Canyon. At its base, around −19 m, a very low bedding-plane passage begins.

This low passage defines the character of the cave. Historical exploration reports describe an average height of about 40 cm. Around 2001, explorers progressed through the low section with cylinders carried at their sides. Exploration then continued to about 400 m, where a dry chamber was reached. Farther on, submerged passages resume, with shafts reaching approximately −38 m. At around 770 m from the entrance, a large underground lake was reached.

From personal experience: the first section can be dived with a 2×7 L / 300 bar backmount configuration, but farther in the passage becomes so low that continuing in backmount is impractical. A compact sidemount configuration is necessary for further penetration.