Linked from
The 14 pages that link to Jet propulsion, each with the reason it gives.
LocomotionRelated: Squid and some other animals use expelled water for rapid movement.
CephalopodRelated: Most cephalopods use mantle contractions and a funnel to swim this way.
Giant squidRelated: The giant squid moves by forcing water through its siphon.
Common octopusRelated: The common octopus uses water expelled through its siphon for rapid escape.
NautiloidRelated: Nautiloids move through water using the cephalopod funnel.
SalpRelated: Water expelled during feeding also drives a salp forward.