This line of professional diver watches is suited for a variety of diving options - from snorkeling to scuba diving to saturation diving. While the 2ER00001B diver watch has a water resistance of up to 100m (perfect for snorkeling), the CEM65001B and CEM75001B diver watches have a water resistance of up to 200m (great for dives without helium). With a water resistance of up to 300m, the CFD0C001B Professional Saturation Diver watch, a watch compatible with saturation diving, is primarily aimed at the specialized diving used for deep-sea salvage and oilfield drilling. Saturation diving involves exposing a diver to helium prior to a long dive to prevent nitrogen narcosis. Helium gas molecules could penetrate a regular water resistant watch, raising internal pressure, causing the watch to break when surfacing. To prevent this, most watches have an escape valve or are specially designed to avoid helium penetration. The CFD0C001B Professional Saturation Diver watch has a special case design to prevent the helium gas from penetrating and in turn, the internal pressure from rising. Therefore, there is no need for an escape valve.