Some interpret this as meaning total immersion or submersion beneath the water. Others speak of early Christians as baptizing either by submersion or by immersion. The notion of a submersion is dual to the notion of an immersion. Since the 18th century immersion and submersion became more widespread. They interpret some Biblical passages concerning baptism as requiring submersion of the body in water. Transformers designed for below-grade installation can be designed for periodic submersion in water. Submersion, particularly of the face, in cold water, triggers a response called the diving reflex. Tests showed that even after 100 hours of submersion, the buoyancy was still effective. Chemical pre-treatments involve the use of phosphates or chromates in submersion or spray application. Rugged compact cameras typically include protection against submersion, hot and cold conditions, shock and pressure. The archipelago is low-lying and is prone to substantial submersion in severe weather. In Riemannian geometry, this is used in the definition of a Riemannian submersion. A good submersion liquid is Fluorinert made by 3M, which is expensive. If properly cleaned and cured, it holds up well over extended periods of submersion. Paintings of the submersion of Atlantis are comparatively rare.