You're looking at the world's largest swimming pool in the San Alfonso del Mar resort in Algarrobo, Chile. The pool's more than 1,000 yards (914 m) long, covers 20 acres and holds about 66 million gallons (250,000 m3) of water:
The man-made saltwater lagoon has been attracting huge crowds to the San Alfonso del Mar resort at Algarrobo, on Chile's southern coast, since it opened last month.
Its turquoise waters are so crystal clear that you can see the bottom even in the deep end.
It dwarfs the world's second biggest pool, the Orthlieb – nicknamed the Big Splash – in Morocco, which is a mere 150 yards long and 100 yards wide. An Olympicsize pool measures some 50 yards by 25 yards.
Chile's monster pool uses a computer- controlled suction and filtration system to keep fresh seawater in permanent circulation, drawing it in from the ocean at one end and pumping it out at the other.
Link - Thanks Another Jake, indeed it was neat!