Liquid Lake on Titan

Sadly you won’t be able to swim in this lake as it’s made of ethane which is a liquid solution of methane, nitrogen and other low-molecular weight hydrocarbons:

Cassini instrument confirms liquid surface lake on Titan

“Scientists have confirmed that at least one body in our solar system, other than Earth, has a surface liquid lake. Using an instrument on NASA’s Cassini orbiter, they discovered that a lake-like feature in the south polar region of Saturn’s moon, Titan, is truly wet. The lake is about 235 kilometers, or 150 miles, long.”