Details from NASA’s Jet Propulsion Laboratory at Cal Tech:
These images from the Radar instrument aboard NASA’s Cassini spacecraft show the evolution of a transient feature in the large hydrocarbon sea named Ligeia Mare on Saturn’s moon Titan.
Analysis by Cassini scientists indicates that the bright features, informally known as the “magic island,” are a phenomenon that changes over time. They conclude that the brightening is due to either waves, solids at or beneath the surface or bubbles, with waves thought to be the most likely explanation. They think tides, sea level and seafloor changes are unlikely to be responsible for the brightening.
The images in the column at left show the same region of Ligeia Mare as seen by Cassini's radar during flybys in (from top to bottom) 2007, 2013, 2014 and 2015. … These features are the first instances of active processes in Titan’s lakes and seas to be confirmed by multiple detections.
(See all Orbital Views here)