La Coronilla

The town of la Coronilla has seen better times. Less than a half mile south of town there is a canal that was dug in 1920 to drain run off from farm land higher up. There is no real highlands in Uruguay, and around 1980, the canal was connected to thousands of acres of swamp land in an effort to stimulate agriculture. The brackish water that continues to pour into the sea there has turned the tide an ugly brown. The high concentration of vegetable matter is churned into a scummy foam that the current takes directly into La Coronilla's beaches. Roughly a half dozen large resort hotels sit abandoned on the town's beaches--a sad reminder of better days. The Parque Oceanica--a mile or so south--is unaffected by the tides (although I still don't think that I would go in the water). One of the few hotels that remain in the town offers "safaris" on the beach's dunes.
See gramps do some safariing of his own on the beach.
 The crucial coastline of Uruguay was fiercely contested by Spain and Portugal, and remnants of that struggle remain. Fortaleza Santa Teresa, a few miles south of La Coronilla, was begun by the Portuguese but completed by the Spanish. Its strategic location on a hill top about a mile from the shore minimized the damage from smaller ship's guns. 
The walls there are between 7 and 10 feet thick.