
San alfonso del Mar pool, By Crystal Lagoons (Own work) [CC-BY-SA-3.0], via Wikimedia Commons
San Alfonso del Mar is a private resort in Algarrobo, Chile, about 100 km west of the capital Santiago.

San alfonso del Mar pool beach, via Planet Apex
This magnificent piece of architecture is 1013 m long, covering 8 ha (20 acres),containing some 250,000,000 litres of seawater, with a maximum depth of 35 m (115 ft). The water is pumped from the Pacific Ocean, filtered, and treated.
Swimming in the ocean is banned here.