When we lived on the Atlantic coast of Uruguay for eight months or so (serious safety issues forcing us to leave) I spent a day in December visiting the remote coastal town Cabo Polonio.
Out of all the beach towns I visited in the country, this one was tops for tranquility, fun (have to take a 4-wheel jeep or ride a horse to get there from the highway; pretty darn fun) and rustic beach cabins.
A highlight is to walk to the lovely lighthouse, then wander through the brush-lined dirt paths to the seafront below to visit the sea lions.
The day I went there was a pro kiteboarder showing off in the bay, the end of the video has him sailing up into the air then crashing back down on the rumbling waves… what they did over and over again… amazing stamina and yes, I was very jealous!