Squid move by pumping water in and out of their bodies. Propulsion comes from using the water itself, sucked into the mantle and squeezed out through a smaller tube called a siphon in a series of strong pulses. By finely manipulating their siphons, squid maintain precise control the water stream: volume, intensity, and direction. All cephalopods carry siphons, even the lumbering octopus, but squid get the most mileage from them.
Water is heavy, so you’d expect slow acceleration from a squid. Not so: powerful rings of muscle surround the mantle, squeezing a huge amount of water through the siphon and creating large accelerations. They’ve also got a secret weapon for emergencies: a lightning-fast escape mechanism.