To exit the simulation and return to the surface at any time press the BACK button. A pop-up menu will appear, giving you the option of saving or not saving the dive. If you select Save, a safe ascent profile will be drawn to the surface, including any decompression stops, deep stops, or safety stops. If any gas switch alerts are set, the gas switches will be automatically made. The dive will be saved in the Sim Dive Log, and you will be returned to the Simulation Menu.
Click here for more information on simulating decompression dives or multi-gas dives.