This robot prototype was built at NASA’s Jet Propulsion Laboratory in Southern California to demonstrate the feasibility of a mission concept called SWIM, short for Sensing With Independent Micro-swimmers. SWIM envisions a swarm of dozens of self-propelled, cellphone-size robots exploring the waters of icy moons like Jupiter’s Europa and Saturn’s Enceladus.
https://www.nasa.gov/image-detail/pia26423orig/