"Nautilus" uses floodable tanks in order to adjust buoyancy and so control its depth. The pumps that evacuate these tanks of water are so powerful that they produce large jets of water when the vessel emerges rapidly from the surface of the water. This leads many early observers of "Nautilus" to believe that the vessel is some species of marine mammal, or perhaps a sea monster not yet known to science. To submerge deeply in a short time, "Nautilus" uses a technique called "hydroplaning", in which the vessel dives down at a steep angle.