Several animals can move by jet propulsion, and they are all mollusks belonging to the class Cephalopod. This group of mollusks include the octopuses, squid and cuttlefishes.
Cephalopods draw in water from the sea by means of slits in the body wall. The water is then drawn over the gills so that the animals can breathe. When the water is pumped violently out of the body by means of a tube called the siphon, it causes the animal to shoot along by jet propulsion. By altering the direction of the siphon, the animal can move in any direction it wishes. It used this method particularly to escape from predators.
Inflation. This is not the only method these animals have for escaping. Anyone who has tried to prise an octopus from a rocky crevice will know how hard this is. The animal inflates its body to wedge itself in, and can also grip the rock with its powerful suckered tentacles.
Camouflage Ceohalopods can also change their body color to match their surroundings, and so remain undetected. Also, they can squirt a dark inky substance into the water while they make their “jet-propelled” escape.