Enceladus, a moon of Saturn, probably has a saltwater ocean under it’s surface, at least per an analysis of data from the Cassini probe. Take it away NASA and JPL:

For the first time, scientists working on NASA’s Cassini mission have detected sodium salts in ice grains of Saturn’s outermost ring. Detecting salty ice indicates that Saturn’s moon Enceladus, which primarily replenishes the ring with material from discharging jets, could harbor a reservoir of liquid water — perhaps an ocean — beneath its surface.

Such an ocean would vastly increase the chance of life elsewhere in our solar system, beyond our own planet.