A vehicle snorkel is the land-based equivalent of the submarine snorkel which allows submarines to use diesel engines while submerged. Snorkels, when used by vehicles with air-breathing internal combustion engines, sometimes allow limited deep wading capability for river crossing or amphibious landing operations, particularly in the case of tanks and other armored vehicles. In such cases, the snorkel supplies air for both the engine and the sealed crew compartment, allowing total submersion. Often, the snorkel pipe is of large diameter and fits over the crew hatch, to provide an escape route for the crew in case the vehicle becomes stuck or disabled while underwater.