mystery island on Titan

http://www.space.com/26325-cassini-titan-waves-magic-island.html

For years, scientists have puzzled over an anomalous feature in radar imagery of Ligeia Mare, a hydrocarbon-filled lake on the Saturnian moon Titan. A bright, seemingly solid spot appeared out of nowhere in July 2013, in an image from the Cassini orbiter's Synthetic Aperture Radar — but it failed to show up during subsequent flybys. That led some scientists to nickname the feature "Magic Island."

jpr: Looks like tidal action to me!