This creates a suction and pulls in water through the space located between the anterior edge of the mantle and the head. When the mantle cavity is full the increasing pressure created by the water causes the circular muscles to contract that in turn closes the opening through which the water entered. The longitudinal muscles then contract and force the water through the ventral tubular funnel. The force of the expelled water as it leaves the funnel propels the animal in the opposite direction. This funnel is also quite mobile, allowing the animal to maneuver either backwards or forwards.
Speed depends on how forcibly the water is expelled.
Squid are able to hover or dart away very quickly. In normal swimming, the arms are stretched anteriorly and held closely together. Their fins are extended and they undulate gently. These fins wrap tightly against the body during rapid swimming. Nautilus can also swim with surprising speed.