A bathyscaphe (/ˈbæθɨskeɪf/ or /ˈbæθɨskæf/) is a free-diving self-propelled deep-sea submersible, consisting of a crew cabin similar to a bathysphere, but suspended below a float rather than from a surface cable, as in the classic bathysphere design.The float is filled with gasoline because it is readily available, buoyant, and, for all practical purposes, incompressible.