San Alfonso del Mar is a private resort in Algarrobo, Chile, and it boasts the world's largest swimming pool, at 0.629-miles long, covering 20 acres, and containing some 66,000,000 US gal of seawater. It has a maximum depth of 35 m (115 ft) and the water is pumped, filtered, and treated from the Pacific Ocean. The pool was developed by Fernando Fischmann and his Chilean company Crystal Lagoons. It's estimated to have cost $1.5-billion to $2-billion total to build, with almost $4-million in annual maintenance. Continue reading for a video and more pictures.