It is more than 1,000 yards long, covers 20 acres, had a 115ft deep end and holds 66 million gallons of water.

Yesterday the Guinness Book of Records named the vast pool beside the sea in Chile as the biggest in the world.

But if you fancy splashing out on one of your own - and you have the space to accommodate it - then beware: This one took five years to build, cost nearly 1billion and the annual maintenance bill will be 2million.

The man-made saltwater lagoon has been attracting huge c rowds to the San Alfonso del Mar resort at Al garrobo, 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.

The sun warms the water to 26c, nine degrees warmer than the adjoining sea.

Chilean biochemist Fernando Fischmann, whose Crystal Lagoons Corporation designed the pool, said advanced engineering meant his company could build "an impressive artificial paradise" even in inhospitable areas.

"As long as we have access to unlimited seawater, we can make it work, and it causes no damage to t he oce an."